Using PHP’s array_key_first() Function to Retrieve the First Key of an Array
This article explains the PHP 7.3+ array_key_first() function, shows its syntax and a practical example for obtaining the first key of an associative array, and provides a fallback method using array_keys() for older PHP versions.
PHP is a widely used server‑side scripting language and functions are essential to its programming; the array_key_first() function, introduced in PHP 7.3, returns the first key of an array.
The function’s syntax is: array_key_first(array $array): mixed In the example, an associative array $students is defined with names as keys and ages as values. The call $first_key = array_key_first($students); stores the first key ("Tom") in $first_key, which is then echoed to produce the output "第一个学生的姓名是：Tom".
If the PHP version is lower than 7.3, array_key_first() is unavailable; the same result can be achieved by retrieving all keys with array_keys($students) and selecting the first element, as shown in the alternative code snippet.
Both approaches allow developers to flexibly obtain the first key of an array, facilitating further array manipulation.
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