In PHP, array_key_first() gets the first key of an array
In PHP, array_key_first () gets the first key of an array however, it does not affect the internal array pointer. It was introduced in PHP 7.3.0.
Migrated function of PHP from PHP 7.2.x to PHP 7.3.x
Migrated function of PHP from PHP 7.2.x to PHP 7.3.x.
What are the new features in PHP 7.2
Features of PHP 7.3