The PHP array_push function adds one or more values to the end of an array. As you can see in the description, the array is passed by reference, meaning that this function will modify the original array.

The PHP function array_pop removes the last element from an array and returns the removed element

The PHP function array_pad takes an array and extends it to a specific length by filling it with a specified value.

The function PHP array_merge_recursive Merge one or more arrays recursively

The PHP array_merge function combines 2 or more arrays, resulting in a new array.