(PHP 4 >= 4.0.7, PHP 5, PHP 7, PHP 8)
array_key_exists — 检查数组里是否有指定的键名或索引
数组里有键 key 时，array_key_exists() 返回 true。
key
可以是任何能作为数组索引的值。
key要检查的键。
array一个数组，包含待检查的键。
| 版本 | 说明 |
|---|---|
| 8.0.0 |
key 参数现在接受
bool、float、int、null、resource
和 string 作为参数。
|
示例 #1 array_key_exists() 示例
<?php
$search_array = array('first' => 1, 'second' => 4);
if (array_key_exists('first', $search_array)) {
echo "The 'first' element is in the array";
}
?>注意:
由于为了兼容以前版本，如果 object 当做
array传入 array_key_exists()，同时key是对象的属性，也会返回true。 此行为在 PHP 7.4.0 弃用且在 PHP 8.0.0 移除。要检查对象是否有某个属性，应该使用 property_exists()。
In PHP7+ to find if a value is set in a multidimensional array with a fixed number of dimensions, simply use the Null Coalescing Operator: ??So for a three dimensional array where you are not sure about any of the keys actually existing<?php// instead of:$exists = array_key_exists($key1, $arr) && array_key_exists($key2, $arr[$key1]) && array_key_exists($key3, $arr[$key1][$key2]) ;// use:$exists = array_key_exists($key3, $arr[$key1][$key2]??[]) ;?>When you want to check multiple array keys: <?php$array = [];$array['a'] = '';$array['b'] = '';$array['c'] = '';$array['d'] = '';$array['e'] = '';// all given keys a,b,c exists in the supplied arrayvar_dump(array_keys_exists(['a','b','c'], $array)); // bool(true)function array_keys_exists(array $keys, array $array): bool{ $diff = array_diff_key(array_flip($keys), $array); return count($diff) === 0;}<?php// Define an associative array$userProfile = [ 'name' => 'John Doe', 'email' => 'john.doe@example.com', 'age' => 30, 'country' => 'USA'];// Key to check$keyToCheck = 'email';// Use array_key_exists to check if the key exists in the arrayif (array_key_exists($keyToCheck, $userProfile)) { echo "The key '$keyToCheck' exists in the array with value: " . $userProfile[$keyToCheck];} else { echo "The key '$keyToCheck' does not exist in the array.";}?><?php// Define an associative array$userProfile = [ 'name' => 'John Doe', 'email' => 'john.doe@example.com', 'age' => 30, 'country' => 'USA'];// Key to check$keyToCheck = 'email';// Use array_key_exists to check if the key exists in the arrayif (array_key_exists($keyToCheck, $userProfile)) { echo "The key '$keyToCheck' exists in the array with value: " . $userProfile[$keyToCheck];} else { echo "The key '$keyToCheck' does not exist in the array.";}?>