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PHP
1
Print a literal string on standard output
echo "Hello World" . PHP_EOL;
Alternative implementation:
<?='Hello World'?>
Alternative implementation:
<?php echo 'Hello World'; ?>
2
Loop to execute some code a constant number of times
for ($i = 0; $i < 10; $i++) {
    echo 'Hello' . PHP_EOL;
}
Alternative implementation:
foreach(range(1, 10) as $i)
  echo 'Hello'. PHP_EOL;
3
Like a function which doesn't return any value, thus has only side effects (e.g. Print to standard output)
function finish($name) 
{
    echo "My job here is done. Goodbye $name";
}
Alternative implementation:
function()
{
    echo "Hello World";
}
4
Create a function which returns the square of an integer
function square(int $x): int
{
    return $x * $x;
}

// square(4) -> 16
// square(3.4) -> Uncaught TypeError: Argument 1 passed to square() must be of the type int, float given
5
Declare a container type for two floating-point numbers x and y
class Point
{
    /** @var float */
    public $x = 0.0;

    /** @var float */
    public $y = 0.0;
}
6
Do something with each item x of the list (or array) items, regardless indexes.
foreach ($items as $x){
    doSomething( $x );
}
Alternative implementation:
array_map(func, $items);
7
Print each index i with its value x from an array-like collection items
foreach ($items as $i=>$x)
{
    echo "i=$i, x=$x"; echo '<br>';
}
8
Create a new map object x, and provide some (key, value) pairs as initial content.
$x = ['one' => 1, 'two' => 2];
9
The structure must be recursive because left child and right child are binary trees too. A node has access to children nodes, but not to its parent.
class BNode
{
    public $data;
    public $lNode;
    public $rNode;

    public function __construct($item)
    {
        $this->data = $item;
        $this->lNode = null;
        $this->rNode = null;
    }
}
10
Generate a random permutation of the elements of list x
shuffle($x);
11
The list x must be non-empty.
$x[ array_rand($x) ]
12
Check if the list contains the value x.
list is an iterable finite container.
in_array($x, $list, true);
13
Access each key k with its value x from an associative array mymap, and print them.
foreach ($mymap as $k=>$x)
{
    echo "Key=$k, Value=$x <br>";
}
14
Pick a random number greater than or equals to a, strictly inferior to b. Precondition : a < b.
function pick(float $a, float $b): float
{
    $rand = mt_rand() / mt_getrandmax();
    $rand *= ($b - $a);
    $rand += ($a);

    return $rand;
}
15
Pick a random integer greater than or equals to a, inferior or equals to b. Precondition : a < b.
rand($a, $b)
16
Call a function f on every node of binary tree bt, in depth-first infix order
public function dfs($f, $bt)
{
	if ($bt->left != null)
		$this->dfs($f, $bt->left);

	$f($bt);
	
	if ($bt->right != null)
		$this->dfs($f, $bt->right);
}
17
The structure must be recursive. A node may have zero or more children. A node has access to its children nodes, but not to its parent.
class Tree
{
    public $children = [];
    public $data;
    
    public function __construct($data, $children)
    {
        $this->data = $data;
        $this->children = $children;
    }
}
Alternative implementation:
final class Node {
    public function __construct(public array $children, public mixed $data) {}
}
18
Call a function f on every node of a tree, in depth-first prefix order
function dfs($f, $root)
{
    $f($root);
    foreach($root as $child)
    {
        dfs($child);
    }	
}
19
Reverse the order of the elements of the list x.
This may reverse "in-place" and destroy the original ordering.
$x = array_reverse($x, true);
20
Implement a function search which looks for item x in a 2D matrix m.
Return indices i, j of the matching cell.
Think of the most idiomatic way in the language to return the two values at the same time.
function search($x, array $m): ?array
{
    for ($j = 0; $j < count($m); $j++) {
        if (($i = array_search($x, $m[$j])) !== false) {
            return [$i, $j];
        }
    }

    return null;
}
21
Swap the values of the variables a and b
$tmp = $a;
$a = $b;
$b = $tmp;
Alternative implementation:
list($b, $a ) = [ $a, $b ];
Alternative implementation:
[ $b, $a ] = [ $a, $b ];
22
Extract the integer value i from its string representation s (in radix 10)
$i = intval($s, 10);
23
Given a real number x, create its string representation s with 2 decimal digits following the dot.
$s = sprintf('%.2f', $x);
24
Declare a new string s and initialize it with the literal value "ネコ" (which means "cat" in japanese)
$s = "ネコ";
25
Share the string value "Alan" with an existing running process which will then display "Hello, Alan"
class AsyncOperation extends Thread
{
    private $name;

    public function __construct($arg)
    {
        $this->name = $arg;
    }

    public function run()
    {
        sleep(1);
        if ($this->name) {
            printf("Hello %s\n", $this->name);
        }
    }
}

$thread = new AsyncOperation("World");

if ($thread->start()) {
    $thread->merge(['name' => 'Alan']);
}
26
Declare and initialize a matrix x having m rows and n columns, containing real numbers.
$x = array();
$x = array_pad($x, m, 1);
for($i = 0; $i < count($x); $i++){
  $x[$i] = array();
  $x[$i] = array_pad($x[$i],n,1);
}
Alternative implementation:
$m = 3;
$n = 4;

$x = array_map(
    function () use ($m) { return array_fill(0, $m, 0); },
    range(1, $n)
);
27
Declare and initialize a 3D array x, having dimensions boundaries m, n, p, and containing real numbers.
$x = array_fill(0, $m, array_fill(0, $n, array_fill(0,$p,0)));
28
Sort the elements of the list (or array-like collection) items in ascending order of x.p, where p is a field of the type Item of the objects in items.
function cmp($a, $b)
{
    if ($a->p == $b->p) {
        return 0;
    }

    return ($a->p < $b->p) ? -1 : 1;
}

usort($items, 'cmp');
29
Remove i-th item from list items.
This will alter the original list or return a new list, depending on which is more idiomatic.
Note that in most languages, the smallest valid value for i is 0.
unset($items[$i]);
31
Create the recursive function f which returns the factorial of the non-negative integer i, calculated from f(i-1)
function f($i) {
	if($i == 0) {
		return 1;
	}

	return ($i * f($i-1));
}
Alternative implementation:
function f(int $i): int
{
    if ($i == 0) {
        return 1;
    }

    return $i * f($i - 1);
}
32
Create function exp which calculates (fast) the value x power n.
x and n are non-negative integers.
function custom_exp($x, $n)
{
    if ($n === 0) {
        return 1;
    }

    if ($n === 1) {
        return $x;
    }

    if (!($n % 2)) {
        return custom_exp($x * $x, $n / 2);
    }

    return $x * custom_exp($x * $x, ($n - 1) / 2);
}

echo custom_exp(5, 10);
33
Assign to the variable x the new value f(x), making sure that no other thread may modify x between the read and the write.
$mutex = Mutex::create();
Mutex::lock($mutex);
$x = f($x);
Mutex::unlock($mutex);
Mutex::destroy($mutex);
35
Implement a function compose (A -> C) with parameters f (A -> B) and g (B -> C), which returns the composition function g ∘ f
function compose($f, $g)
{
    return function ($x) use ($f, $g) {
        return $g($f($x));
    };
};
36
Implement a function compose which returns composition function g ∘ f for any functions f and g having exactly 1 parameter.
function compose($f,$g){
	return function($x) use($f,$g) {
		return $g($f($x));
	}
}
37
Transform a function that takes multiple arguments into a function for which some of the arguments are preset.
function curry($f, ...$argsCurried)
{
    return function (...$args) use ($f, $argsCurried) {
        $finalArgs = array_merge($argsCurried, $args);
        return call_user_func_array($f, $finalArgs);
    };
}

function add($n1, $n2)
{
    return $n1 + $n2;
}

$addFive = curry('add', 5);

echo $addFive(2), PHP_EOL;
echo $addFive(-5), PHP_EOL;
Alternative implementation:
function curry($f, ...$argsCurried)
{
    return function (...$args) use ($f, $argsCurried) {
        return $f(...$argsCurried, ...$args);
    };
}

function add($n1, $n2)
{
    return $n1 + $n2;
}

$addFive = curry('add', 5);

echo $addFive(2), PHP_EOL;
echo $addFive(-5), PHP_EOL;
38
Find substring t consisting in characters i (included) to j (excluded) of string s.
Character indices start at 0 unless specified otherwise.
Make sure that multibyte characters are properly handled.
$t = mb_substr($s, $i, $j-$i, 'UTF-8');
39
Set the boolean ok to true if the string word is contained in string s as a substring, or to false otherwise.
$mystring = 'abc';
$findme   = 'a';
$pos = strpos($mystring, $findme);

// Nótese el uso de ===. Puesto que == simple no funcionará como se espera
// porque la posición de 'a' está en el 1° (primer) caracter.
if ($pos === false) {
    echo "La cadena '$findme' no fue encontrada en la cadena '$mystring'";
} else {
    echo "La cadena '$findme' fue encontrada en la cadena '$mystring'";
    echo " y existe en la posición $pos";
}
Alternative implementation:
$mystring = 'abc';
$findme   = 'a';
$pos = strpos($mystring, $findme);

// Nótese el uso de ===. Puesto que == simple no funcionará como se espera
// porque la posición de 'a' está en el 1° (primer) caracter.
if ($pos === false) {
    echo "La cadena '$findme' no fue encontrada en la cadena '$mystring'";
} else {
    echo "La cadena '$findme' fue encontrada en la cadena '$mystring'";
    echo " y existe en la posición $pos";
}
Alternative implementation:
$ok = str_contains($s, $word);
41
Create the string t containing the same characters as the string s, in reverse order.
The original string s must remain unaltered. Each character must be handled correctly regardless its number of bytes in memory.
for ($i=0;$i<mb_strlen($s);$i++) {
    $characters[] = mb_substr($s, $i, 1, 'UTF-8');
}

$characters = array_reverse($characters);
$t = implode($characters);
42
Print each item v of list a which is not contained in list b.
For this, write an outer loop to iterate on a and an inner loop to iterate on b.
$array_1 = [1,2,3,4,5];
$array_2 = [3,4];

foreach ($array_1 as $a) {
    foreach ($array_2 as $b) {
        if ($b == $a) {
            continue 2;
        }
    }
    echo $a
}
43
Look for a negative value v in 2D integer matrix m. Print it and stop searching.
for ($y = 0; $y < count($m); $y++) {
    for ($x = 0; $x < count($m[$y]); $x++) {
        if ($m[$y][$x] == $v) {
            break 2;
        }
    }
}
44
Insert the element x at position i in the list s. Further elements must be shifted to the right.
array_splice($s, $i, 0, $x);
45
Sleep for 5 seconds in current thread, before proceeding with the next instructions.
sleep(5);
46
Create the string t consisting of the 5 first characters of the string s.
Make sure that multibyte characters are properly handled.
$t = mb_substr($s, 0, 5, 'UTF-8');
47
Create string t consisting in the 5 last characters of string s.
Make sure that multibyte characters are properly handled.
$t = mb_substr($s, -5, null, 'UTF-8');
48
Assign to variable s a string literal consisting in several lines of text, including newlines.
$s = "This string 
is spanning
three lines";
Alternative implementation:
$s = <<<EOD
Huey
Dewey
Louie
EOD;
49
Build list chunks consisting in substrings of the string s, separated by one or more space characters.
$chunks = preg_split('/ +/', $s);
50
Write a loop that has no end clause.
while (true) {
    // do something
}
51
Determine whether the map m contains an entry for the key k
array_key_exists($k, $m)
52
Determine whether the map m contains an entry with the value v, for some key.
in_array($v, $m, true);
53
Concatenate elements of string list x joined by the separator ", " to create a single string y.
$y = implode(', ', $x);
54
Calculate the sum s of the integer list or array x.
$s = array_sum($x);
55
Create the string representation s (in radix 10) of the integer value i.
$s = "$i";
Alternative implementation:
$s = (string)$i;
Alternative implementation:
$s = "{$i}";
Alternative implementation:
$s = strval($i);
57
Create the list y containing the items from the list x that satisfy the predicate p. Respect the original ordering. Don't modify x in-place.
function p($element) {  /* .... */ }

$y = array_filter ($x, "p");
58
Create the string lines from the content of the file with filename f.
$lines = file_get_contents('f');
if ($lines === false) {
    // handle error...
}
59
Print the message "x is negative" to standard error (stderr), with integer x value substitution (e.g. "-2 is negative").
fwrite(STDERR, "{$x} is negative\n");
60
Assign to x the string value of the first command line parameter, after the program name.
$x = $argv[1];
61
Assign to the variable d the current date/time value, in the most standard type.
$d = time();
62
Set i to the first position of string y inside string x, if exists.

Specify if i should be regarded as a character index or as a byte index.

Explain the behavior when y is not contained in x.
$i = mb_strpos($x, $y, 0, 'UTF-8');
63
Assign to x2 the value of string x with all occurrences of y replaced by z.
Assume occurrences of y are not overlapping.
$x2 = str_replace($y, $z, $x);
64
Assign to x the value 3^247
$x = gmp_pow(3, 247);
echo gmp_strval($x);
65
From the real value x in [0,1], create its percentage string representation s with one digit after decimal point. E.g. 0.15625 -> "15.6%"
$s = number_format($x * 100.0, 1) . '%';
67
Calculate binom(n, k) = n! / (k! * (n-k)!). Use an integer type able to handle huge numbers.
gmp_binomial($n, $k);
68
Create an object x to store n bits (n being potentially large).
$x = new BitSet($n);
69
Use seed s to initialize a random generator.

If s is constant, the generator output will be the same each time the program runs. If s is based on the current value of the system clock, the generator output will be different each time.
srand($s);
70
Get the current datetime and provide it as a seed to a random generator. The generator sequence will be different at each run.
srand(time());
71
Basic implementation of the Echo program: Print all arguments except the program name, separated by space, followed by newline.
The idiom demonstrates how to skip the first argument if necessary, concatenate arguments as strings, append newline and print it to stdout.
echo implode(' ', array_slice($argv, 1)), PHP_EOL;
74
Compute the greatest common divisor x of big integers a and b. Use an integer type able to handle huge numbers.
$x = gmp_gcd($a, $b);
75
Compute the least common multiple x of big integers a and b. Use an integer type able to handle huge numbers.
$gcd = gmp_lcm($a, $b);
echo gmp_strval($gcd);
76
Create the string s of integer x written in base 2.

E.g. 13 -> "1101"
$s = sprintf("%b", $x);
78
Execute a block once, then execute it again as long as boolean condition c is true.
do {
    echo '.';
} while ($c);
79
Declare the floating point number y and initialize it with the value of the integer x .
$y = (float) $x;
80
Declare integer y and initialize it with the value of floating point number x . Ignore non-integer digits of x .
Make sure to truncate towards zero: a negative x must yield the closest greater integer (not lesser).
$y = (int)$x;
81
Declare the integer y and initialize it with the rounded value of the floating point number x .
Ties (when the fractional part of x is exactly .5) must be rounded up (to positive infinity).
$y = (int) round($x);
82
Find how many times string s contains substring t.
Specify if overlapping occurrences are counted.
$c = substr_count($s , $t);
83
Declare regular expression r matching the strings "http", "htttp", "httttp", etc.
preg_match_all("/htt+p/", $r, $matches)
84
Count number c of 1s in the integer i in base 2.

E.g. i=6 → c=2
$i = base_convert($i,10,2);
$x = str_replace(0,'',$i);
$c = strlen($x);
85
Write boolean function addingWillOverflow which takes two integers x, y and return true if (x+y) overflows.

An overflow may be above the max positive value, or below the min negative value.
function _addingWillOverflow($x, $y): bool
{
    return (PHP_INT_MAX - $y) > $x;
}
86
Write the boolean function multiplyWillOverflow which takes two integers x, y and returns true if (x*y) overflows.

An overflow may reach above the max positive value, or below the min negative value.
function multiplyWillOverflow($x, $y)
{
      return ($x * $y) > PHP_INT_MAX;
}
87
Exit immediately.
If some extra cleanup work is executed by the program runtime (not by the OS itself), describe it.
exit();
Alternative implementation:
die();
88
Create a new bytes buffer buf of size 1,000,000.
$memStart = memory_get_usage();
$buf = str_repeat("\x00", 1000 * 1000);
$memEnd = memory_get_usage();
echo $memEnd - $memStart, PHP_EOL;
89
You've detected that the integer value of argument x passed to the current function is invalid. Write the idiomatic way to abort the function execution and signal the problem.
throw new \InvalidArgumentException($x . ' is invalid.');
90
Expose a read-only integer x to the outside world while being writable inside a structure or a class Foo.
class Foo
{
    /** @var int */
    private $x;

    /**
     * @return int
     */
    public function getX()
    {
        return $this->x;
    }
}
Alternative implementation:
class Foo
{
    /** @var int */
    private $x;

    public function getX(): int
    {
        return $this->x;
    }
}
91
Read from the file data.json and write its content into the object x.
Assume the JSON data is suitable for the type of x.
$x = json_decode(file_get_contents('data.json'));
92
Write the contents of the object x into the file data.json.
file_put_contents('data.json', json_encode($x));
93
Implement the procedure control which receives one parameter f, and runs f.
function control($f) {
    $f();
}
94
Print the name of the type of x. Explain if it is a static type or dynamic type.

This may not make sense in all languages.
echo is_object($x) ? get_class($x) : gettype($x);
95
Assign to variable x the length (number of bytes) of the local file at path.
$x = filesize($path);
96
Set the boolean b to true if string s starts with prefix prefix, false otherwise.
$b = (bool) preg_match('#^http#', $s);
97
Set boolean b to true if string s ends with string suffix, false otherwise.
$b = (bool)preg_match("/{$suffix}$/", $s);
98
Convert a timestamp ts (number of seconds in epoch-time) to a date with time d. E.g. 0 -> 1970-01-01 00:00:00
$d = DateTime::createFromFormat('U', $ts);
99
Assign to the string x the value of the fields (year, month, day) of the date d, in format YYYY-MM-DD.
$x = date("Y-m-d", strtotime($d));
Alternative implementation:
$formattedVar = date("Y-m-d", strtotime($unformattedVar));

# Take the unformated Variable, let PHP do it's best to
# 'understand' it and then format the resultant into the 
# desired format.
100
Sort elements of array-like collection items, using a comparator c.
uasort($items, $c);
101
Make an HTTP request with method GET to the URL u, then store the body of the response in the string s.
$s = file_get_contents($u);
104
Write the contents of the object x into the file data.xml.
class Test
{
    public $f1;
    private $f2;

    public function __construct($f1, $f2)
    {
        $this->f1 = $f1;
        $this->f2 = $f2;
    }
}

$x = new Test('foo', 42);

$options = array(
  XML_SERIALIZER_OPTION_INDENT        => '    ',
  XML_SERIALIZER_OPTION_RETURN_RESULT => true
  );

$serializer = new XML_Serializer($options);
$result = "<?xml version=\"1.0\"?>\n" . $serializer->serialize($x);
file_put_contents('data.xml', $result);
105
Assign to the string s the name of the currently executing program (but not its full path).
$s = $_SERVER['PHP_SELF'];
106
Assign to string dir the path of the working directory.
(This is not necessarily the folder containing the executable itself)
$dir = getcwd();
107
Assign to string dir the path of the folder containing the currently running executable.
(This is not necessarily the working directory, though.)
$dir = realpath(dirname(__FILE__));
108
Print the value of variable x, but only if x has been declared in this program.
This makes sense in some languages, not all of them. (Null values are not the point, rather the very existence of the variable.)
$x = 'foo';

if (isset($x)) {
    echo $x;
}
Alternative implementation:
if(@$foo) print($foo);
110
Set the boolean blank to true if the string s is empty, or null, or contains only whitespace ; false otherwise.
$blank = (empty(trim($s));
Alternative implementation:
$blank = !trim($s);
111
From current process, run program x with command-line parameters "a", "b".
exec($x . " a b");
112
Print each key k with its value x from an associative array mymap, in ascending order of k.
ksort($mymap);
foreach($mymap as $k => $v) {
    echo 'k:', $k, ' ', 'v:', $v, PHP_EOL;
}
114
Set boolean b to true if objects x and y contain the same values, recursively comparing all referenced elements in x and y.
Tell if the code correctly handles recursive types.
$b = ($x == $y);
115
Set boolean b to true if date d1 is strictly before date d2 ; false otherwise.
$d1 = new DateTime('January 25 2016');
$d2 = new DateTime('January 26 2016');

$b = $d1 < $d2;
116
Remove all occurrences of string w from string s1, and store the result in s2.
$s2 = str_replace($w, '', $s1);
117
Set n to the number of elements of the list x.
$n = count($x);
118
Create the set y from the list x.
x may contain duplicates. y is unordered and has no repeated values.
$y = array_unique($x);
119
Remove duplicates from the list x.
Explain if the original order is preserved.
$x = array_unique($x);
120
Read an integer value from the standard input into the variable n
fscanf(STDIN, "%d\n", $n);
121
Listen UDP traffic on port p and read 1024 bytes into the buffer b.
$socket = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP);
socket_bind($socket, '127.0.0.1', 1337);

socket_recvfrom($socket, $buffer, 16, 0, $fromAddr, $fromPort);
echo "[{$fromAddr}:{$fromPort}]\t{$buffer}";

// Send a test from the command line such as:
// echo "hello" > /dev/udp/127.0.0.1/1337
122
Create an enumerated type Suit with 4 possible values SPADES, HEARTS, DIAMONDS, CLUBS.
abstract class Suit
{
  const SPADES	 = 0;
  const HEARTS	 = 1;
  const DIAMONDS = 2;
  const CLUBS	 = 3;
}
Alternative implementation:
enum Suit
{
    case SPADES;
    case HEARTS;
    case DIAMONDS;
    case CLUBS;
}
123
Verify that predicate isConsistent returns true, otherwise report assertion violation.
Explain if the assertion is executed even in production environment or not.
assert(_isConsistent);
124
Write the function binarySearch which returns the index of an element having the value x in the sorted array a, or -1 if no such element exists.
function binarySearch(array $a, $x)
{
    $imin = 0;
    $imax = count($a) - 1;
    while ($imin <= $imax) {
        $imid = (int)floor($imin + ($imax-$imin) / 2);
        if ($a[$imid] === $x) {
            return $imid;
        }
        if ($a[$imid] < $x) {
            $imin = $imid + 1;
        } else {
            $imax = $imid - 1;
        }
    }
    return -1;
}
125
measure the duration t, in nanoseconds, of a call to the function foo. Print this duration.
$start = hrtime(true);
foo();
$end = hrtime(true);
$t = $end - $start;
echo $t;
126
Write a function foo that returns a string and a boolean value.
<?php
function foo() {
    return ['string', FALSE];
}

list($string, $boolean) = foo();
127
Import the source code for the function foo body from a file "foobody.txt".
function foo(): void
{
    include 'foobody.txt';
}
131
Execute f1 if condition c1 is true, or else f2 if condition c2 is true, or else f3 if condition c3 is true.
Don't evaluate a condition when a previous condition was true.
if ($c1) {
  f1();
} else if ($c2) {
  f2();
} else if ($c3) {
  f3();
}
132
Run the procedure f, and return the duration of the execution of f.
$start = microtime(TRUE);
f();
$end = microtime(TRUE);
echo $end - $start, PHP_EOL;
133
Set boolean ok to true if string word is contained in string s as a substring, even if the case doesn't match, or to false otherwise.
$ok = stripos($word, $s) === false;
134
Declare and initialize a new list items, containing 3 elements a, b, c.
$items = [$a, $b, $c];
135
Remove at most 1 item from list items, having the value x.
This will alter the original list or return a new list, depending on which is more idiomatic.
If there are several occurrences of x in items, remove only one of them. If x is absent, keep items unchanged.
$list_position = array_search($x, $items);
$specific_item = $items[$position];
unset($specific_item);
136
Remove all occurrences of the value x from list items.
This will alter the original list or return a new list, depending on which is more idiomatic.
$newItems = array_diff($items, [$x]);
137
Set the boolean b to true if the string s contains only characters in the range '0'..'9', false otherwise.
$b = preg_match('/\D/', $s) !== 1;
138
Create a new temporary file on the filesystem.
$f = tmpfile();
139
Create a new temporary folder on filesystem, for writing.
function createTempDir(): ?string
{
    $path = rtrim(sys_get_temp_dir(), DIRECTORY_SEPARATOR) . DIRECTORY_SEPARATOR . mt_rand() . microtime(true);
    if (mkdir($path)) {
        return $path;
    }
    return null;
}
140
Delete from map m the entry having key k.

Explain what happens if k is not an existing key in m.
unset($m[k]);
141
Iterate in sequence over the elements of the list items1 then items2. For each iteration print the element.
# beginner style
foreach( $items1 as $item ) print "$item\n";
foreach( $items2 as $item ) print "$item\n";

# five times faster
print implode("\n", $items1)."\n".implode("\n", $items2)."\n" ;
142
Assign to string s the hexadecimal representation (base 16) of integer x.

E.g. 999 -> "3e7"
$s = dechex($x);
143
Iterate alternatively over the elements of the lists items1 and items2. For each iteration, print the element.

Explain what happens if items1 and items2 have different size.
# php 5.3+
print array_reduce( array_map( null, $items1, $items2 ), function($c,$d){return $c.($c?"\n":'').implode("\n", $d); }, "")."\n" ;

#php 5.6+
print implode("\n", array_merge( ...array_map( null, $items1, $items2 )))."\n";
144
Set boolean b to true if file at path fp exists on filesystem; false otherwise.

Beware that you should not do this and then in the next instruction assume the result is still valid, this is a race condition on any multitasking OS.
$b = file_exists($fp);
146
Extract floating point value f from its string representation s
$f = floatval($s);
147
Create string t from string s, keeping only ASCII characters
$t = preg_replace('/[^[:ascii:]]/', '', $s);
149
As an exception, this content is not under license CC BY-SA 3.0 like the rest of this website.
 
150
Remove the last character from the string p, if this character is a forward slash /
$p = rtrim($p, '/');
152
Create string s containing only the character c.
$s = (string) $c;
153
Create the string t as the concatenation of the string s and the integer i.
$t = $s . $i;
155
Delete from filesystem the file having path filepath.
unlink($filepath);
156
Assign to the string s the value of the integer i in 3 decimal digits. Pad with zeros if i < 100. Keep all digits if i1000.
$s = sprintf('%03d', $i);
157
Initialize a constant planet with string value "Earth".
const PLANET = 'Earth';
Alternative implementation:
define('PLANET', 'Earth');
158
Create a new list y from randomly picking exactly k elements from list x.

It is assumed that x has at least k elements.
Each element must have same probability to be picked.
Each element from x must be picked at most once.
Explain if the original ordering is preserved or not.
$y = array_intersect_key($x, array_flip(array_rand($x, $k)));
160
Execute f32() if platform is 32-bit, or f64() if platform is 64-bit.
This can be either a compile-time condition (depending on target) or a runtime detection.
<?php

if (PHP_INT_SIZE === 4)
    f32();
else if (PHP_INT_SIZE === 8)
    f64();
161
Multiply all the elements of the list elements by a constant c
array_map(function($v) use ($_c) {
    return $v*$c;
}, $_elements);
163
Print all the list elements, two by two, assuming list length is even.
foreach(array_chunk($list, 2) as $x) {
    echo $x[0], ' ', $x[1], PHP_EOL;
}
165
Assign to the variable x the last element of the list items.
$x = end($items);
Alternative implementation:
$x = $items[array_key_last($items)];
166
Create the list ab containing all the elements of the list a, followed by all the elements of the list b.
$ab = array_merge($a, $b);
167
Create the string t consisting of the string s with its prefix p removed (if s starts with p).
$t = strpos($s, $p) === 0 ? substr($s, strlen($p)) : $s;
168
Create string t consisting of string s with its suffix w removed (if s ends with w).
preg_replace("/{$w}$/u", '', $s);
169
Assign to the integer n the number of characters of the string s.
Make sure that multibyte characters are properly handled.
n can be different from the number of bytes of s.
$n = mb_strlen($s, 'UTF-8');
170
Set n to the number of elements stored in mymap.

This is not always equal to the map capacity.
$n = count($mymap);
171
Append the element x to the list s.
$s[]=$x;
172
Insert value v for key k in map m.
$m[$k] = $v;
173
Number will be formatted with a comma separator between every group of thousands.
echo number_format(1000);
174
Make a HTTP request with method POST to the URL u
$ch = curl_init(); 
curl_setopt($ch, CURLOPT_URL, $u); 
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); 
curl_setopt($ch, CURLOPT_POST, 1);
$output = curl_exec($ch); 
curl_close($ch);
176
From hex string s of 2n digits, build the equivalent array a of n bytes.
Each pair of hexadecimal characters (16 possible values per digit) is decoded into one byte (256 possible values).
$a = array_map('hexdec', str_split($s, 2));
179
Return the center c of the rectangle with coördinates(x1,y1,x2,y2)
class Point
{
	public $x;
	public $y;

	public function __construct(float x, float y)
	{
		$this->x = x;
		$this->y = y;
	}
}

class Rectangle
{
	private $point1;
	private $point2;

	public function __construct(Point $point1, Point $point2)
	{
		$this->point1 = $point1;
		$this->point2 = $point2;
	}

	public function getCenter(): Point
	{
		return new Point(
			($this->point1->x + $this->point2->x) / 2,
			($this->point1->y + $this->point2->y) / 2
		);
	}
}
180
Create the list x containing the contents of the directory d.

x may contain files and subfolders.
No recursive subfolder listing.
$x = scandir($d);
182
Output the source of the current program. A quine is a computer program that takes no input and produces a copy of its own source code as its only output.

Reading the source file from disk is cheating.
<?php $s='<?php $s=%c%s%c;printf($s,39,$s,39);';printf($s,39,$s,39);
183
Make a HTTP request with method PUT to the URL u
<?php

$url = 'http://localhost/tester/log.php';
$ch = curl_init($url);
curl_setopt($ch, CURLOPT_PUT, true);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$fields = array("id" => 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query($fields));
$response = curl_exec($ch);

echo $response;
184
Assign to variable t a string representing the day, month and year of the day after the current date.
$t = date('Y-m-d',strtotime('+1 day'));
Alternative implementation:
$d = new DateTime('tomorrow');
$t = $d->format('Y-m-d');
185
Schedule the execution of f(42) in 30 seconds.
sleep(30);
f(42);
186
Exit a program cleanly indicating no error to OS
exit(0);
189
Produce a new list y containing the result of the function T applied to all elements e of the list x that match the predicate P.
$y = array_map('T', array_filter($x, 'P'));
191
Given a one-dimensional array a, check if any value is larger than x, and execute the procedure f if that is the case
if (count(array_filter($a, function($v) { return $v > $x; })))
  f();

// or with intermediate steps
$tmp = array_filter(
  $a,
  function ($v) { return $v > $x; }
)
if (count($tmp))
  f();

// or with array reduce instead
if (
  array_reduce($a, 
    function($old, $item) { return $old or ($item > $x); }
  )
)
  f();

// Array reduce takes the old result $old, and 
// applies $item (from $a) to the old result 
// iteratively. We use the 'or' boolean operator
// to implement an 'any' operation.
197
Retrieve the contents of file at path into a list of strings lines, in which each element is a line of the file.
$lines = file($path);
if ($lines === false)
  die("Can't open file $path");
198
Abort program execution with error condition x (where x is an integer value)
exit($x);
200
Compute the hypotenuse h of the triangle where the sides adjacent to the square angle have lengths x and y.
$h = hypot($x, $y)

// before PHP 4.1
$h = sqrt($x*$x + $y*$y);
205
Read an environment variable with the name "FOO" and assign it to the string variable foo. If it does not exist or if the system does not support environment variables, assign a value of "none".
$foo = getenv("FOO") ?: "none";
206
Execute different procedures foo, bar, baz and barfl if the string str contains the name of the respective procedure. Do it in a way natural to the language.
switch ($str) {
  case "foo":
    foo();
    break;
  case "bar":
    bar();
    break;
  case "baz":
    baz();
    break;
  case "barfl":
    barfl();
    break;
}
212
Set the boolean b to true if path exists on the filesystem and is a directory; false otherwise.
$b = is_dir($path);
218
Create the list c containing all unique elements that are contained in both lists a and b.
c should not contain any duplicates, even if a and b do.
The order of c doesn't matter.
$c = array_intersect($a, $b)
219
Create the string t from the value of string s with each sequence of spaces replaced by a single space.

Explain if only the space characters will be replaced, or the other whitespaces as well: tabs, newlines.
$t = preg_replace('/\s+/', ' ', $s);
Alternative implementation:
$t = $s;
do $t = str_replace('  ', ' ', $t, $count); while($count);
223
Loop through list items checking a condition. Do something else if no matches are found.

A typical use case is looping through a series of containers looking for one that matches a condition. If found, an item is inserted; otherwise, a new container is created.

These are mostly used as an inner nested loop, and in a location where refactoring inner logic into a separate function reduces clarity.
function search(array $haystack, string $needle, callable $doSuccess, callable $doFail)
{
    foreach ($haystack as $item) {
        if ($item === $needle) {
            $doSuccess();
            return;
        }
    }
    $doFail();
}

$items = ["foo", "bar", "baz", "qux"];
search(
    $items,
    "baz",
    static function () {
        echo "found it";
    },
    static function () {
        echo "not found";
    }
);
224
Insert the element x at the beginning of the list items.
array_unshift($items, $x);
225
Declare an optional integer argument x to procedure f, printing out "Present" and its value if it is present, "Not present" otherwise
function f(?int $x = null) {
    echo $x ? 'Present' . $x : 'Not present';
}
226
Remove the last element from the list items.
array_pop($items);
243
Print the contents of the list or array a on the standard output.
print_r($a)
246
Set c to the number of distinct elements in the list items.
$c = count(array_unique($items));
251
Extract integer value i from its binary string representation s (in radix 2)
E.g. "1101" -> 13
$i = bindec($s);
252
Assign to the variable x the string value "a" if calling the function condition returns true, or the value "b" otherwise.
$x = condition() ? "a" : "b";
255
Print the values of the set x to the standard output.
The order of the elements is irrelevant and is not required to remain the same next time.
echo $x;
256
Print the numbers 5, 4, ..., 0 (included), one line per number.
$values = range(0, 5);
$valuesReversed = array_reverse($values);
foreach($valuesReversed as $value)
{
    printf("%s\n", $value);
}
261
Assign to the string x the value of fields (hours, minutes, seconds) of the date d, in format HH:MM:SS.
$x = $d->format('H:i:s');
266
Assign to the string s the value of the string v repeated n times, and write it out.

E.g. v="abc", n=5 ⇒ s="abcabcabcabcabc"
$s = str_repeat($v, $n);
echo $s;
272
Fizz buzz is a children's counting game, and a trivial programming task used to affirm that a programmer knows the basics of a language: loops, conditions and I/O.

The typical fizz buzz game is to count from 1 to 100, saying each number in turn. When the number is divisible by 3, instead say "Fizz". When the number is divisible by 5, instead say "Buzz". When the number is divisible by both 3 and 5, say "FizzBuzz"
<?php
    for ($n=1; $n<=100; $n++) {
        $out="";
        if ($n%3==0) {
            $out=$out."Fizz";
        }
        if ($n%5==0) {
            $out=$out."Buzz";
        }
        if ($out=="") {
            $out=$out.strval($n);
        }
        echo ($out."\n");
    }
?>
273
Set the boolean b to true if the directory at filepath p is empty (i.e. doesn't contain any other files and directories)
$iterator = new FilesystemIterator($p, FilesystemIterator::SKIP_DOTS);
$b = (iterator_count($iterator) === 0);
287
Assign to n the number of bytes in the string s.

This can be different from the number of characters. If n includes more bytes than the characters per se (trailing zero, length field, etc.) then explain it. One byte is 8 bits.
$n = strlen($s);
289
Create the string s by concatenating the strings a and b.
$s = $a.$b;
302
Given the integer x = 8, assign to the string s the value "Our sun has 8 planets", where the number 8 was evaluated from x.
$s = "Our sun has {$x} planets";
318
Assign to the integer x a random number between 0 and 17 (inclusive), from a crypto secure random number generator.
$x = random_int(0, 17)