array_find_key

(PHP 8 >= 8.4.0)

array_find_key — Returns the key of the first element satisfying a callback function

说明

array_find_key(array $array, callable $callback): mixed

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.

参数

array

The array that should be searched.

callback

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

callback(mixed $value, mixed $key): bool

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

返回值

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.

示例

示例 #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);
}));
?>

以上示例会输出：

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

参见

array_find() - Returns the first element satisfying a callback function
array_all() - Checks if all array elements satisfy a callback function
array_any() - Checks if at least one array element satisfies a callback function
array_filter() - 使用回调函数过滤数组的元素
array_reduce() - 用回调函数迭代地将数组简化为单一的值