array_find_key

Returns the key of the first element satisfying a callback function

説明

mixed array_find_key(array $array, callable $callback)

array_find_key returns the key of the first element of an array for which the given callback returns true. If no matching element is found the function returns null.

パラメータ

array

The array that should be searched.

callback

The callback function to call to check each element, which must be

bool callback(mixed $value, mixed $key)

If this function returns true, the key is returned from array_find_key and the callback will not be called for further elements.

戻り値

The function returns the key of the first element for which the callback returns true. If no matching element is found the function returns null.

例

例1 array_find_key example

<?php
$array = [
    'a' => 'dog',
    'b' => 'cat',
    'c' => 'cow',
    'd' => 'duck',
    'e' => 'goose',
    'f' => 'elephant'
];

// Find the first animal with a name longer than 4 characters.
var_dump(array_find_key($array, function (string $value) {
    return strlen($value) > 4;
}));

// Find the first animal whose name begins with f.
var_dump(array_find_key($array, function (string $value) {
    return str_starts_with($value, 'f');
}));

// Find the first animal where the array key is the first symbol of the animal.
var_dump(array_find_key($array, function (string $value, $key) {
   return $value[0] === $key;
}));

// Find the first animal where the array key matching a RegEx.
var_dump(array_find_key($array, function ($value, $key) {
   return preg_match('/^([a-f])$/', $key);
}));
?>

上の例の出力は以下となります。

string(1) "e"
NULL
string(1) "c"
string(1) "a"

参考

array_find
array_all
array_any
array_filter
array_reduce