Array functions in PHP are built-in functions that are designed to help you work with arrays in PHP. Arrays are a fundamental data structure in PHP that allow you to store and manipulate collections of values.

PHP array functions provide a wide range of tools to work with arrays, including creating arrays, adding and removing elements, sorting and filtering arrays, searching for values in arrays, and merging arrays together. These functions are designed to make it easy to work with arrays in PHP, and can be used to perform complex operations on arrays with just a few lines of code.

PHP has a variety of built-in functions for working with arrays. Some of the most commonly used PHP array functions are:

1. count(): This function is used to Counts the number of elements in an array.
2. in_array(): This function is used to checks if a value exists in an array.
3. array_push(): This function is used to Adds one or more elements to the end of an array.
4. array_pop(): This function is used to Removes and returns the last element of an array.
5. array_shift(): This function is used to Removes and returns the first element of an array.
6. array_unshift(): This function is used to Adds one or more elements to the beginning of an array.
7. array_slice(): This function is used to Extracts a portion of an array.
8. array_merge(): This function is used to Merges two or more arrays into a single array.
9. array_reverse(): This function is used to Reverses the order of elements in an array.
10. array_search(): Searches an array for a given value and returns the corresponding key.
11. array_unique(): This function is used to Removes duplicate values from an array.
12. sort(): This function is used to Sorts an array in ascending order.
13. rsort(): This function is used to Sorts an array in descending order.
14. shuffle(): This function is used to Shuffles the elements of an array randomly.
15. array_key_exists(): Checks if a given key exists in an array.