(PHP 8 >= 8.4.0)
array_find_key — Returns the key of the first element satisfying a callback function
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.
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"