What is difference between array_merge and array_combine?

array_combine() is used to creates a new array by using the key of one array as keys and using the value of another array as values. Whereas array_merge() merges one or more than one array such that the value of second array appended at the end of the first array.

How to check a key exist in an array

PHP array_key_exists() Function is used to check a key exist or not in an array.

Functions available to sort an array in PHP

PHP functions for Sorting Arrays are