Using PHP’s array_key_first() Function to Retrieve the First Array Key

PHP is a widely used server‑side scripting language, and functions are essential; the array_key_first() function was introduced in PHP 7.3 to retrieve the first key of an array.

The syntax is: array_key_first(array $array): mixed The function accepts an array as its argument and returns the first key, or NULL if the array is empty.

Example usage:

$students = array("Tom" => 18, "Jerry" => 19, "Alice" => 20);<br/>$first_key = array_key_first($students);<br/>echo "第一个学生的姓名是：" . $first_key;

In this example, the array $students maps student names to ages; array_key_first() returns the first key ("Tom") which is stored in $first_key and printed.

Note that array_key_first() is only available in PHP 7.3 and later. For earlier versions you can achieve the same result with array_keys():

$students = array("Tom" => 18, "Jerry" => 19, "Alice" => 20);<br/>$keys = array_keys($students);<br/>$first_key = $keys[0];<br/>echo "第一个学生的姓名是：" . $first_key;

This alternative first obtains all keys with array_keys(), selects the first element, and outputs it.

In summary, array_key_first() provides a convenient way to get the first key of an array in PHP 7.3+, while array_keys() can be used as a fallback for older versions.