24. Useful Array Functions

PHP provides hundreds of built-in functions for array manipulation. Mastering these functions is crucial for writing efficient PHP code.

1. Counting and Checking

Function	Description
`count($array)`	Returns the number of elements in an array.
`is_array($var)`	Checks if a variable is an array (returns boolean).
`array_key_exists($key, $array)`	Checks if a specified key exists in an array.

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Function	Description
`array_push($array, $val1, ...)`	Adds elements to the end of an indexed array.
`array_pop($array)`	Removes and returns the element from the end of the array.
`array_unshift($array, $val1, ...)`	Adds elements to the beginning of an array.
`array_shift($array)`	Removes and returns the element from the beginning of the array.

Function	Description
`sort($array)`	Sorts indexed array elements in ascending order (by value).
`rsort($array)`	Sorts indexed array elements in descending order (by value).
`asort($array)`	Sorts associative arrays by value (ascending).
`ksort($array)`	Sorts associative arrays by key (ascending).

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35, 'Joe' => 43, 'Amy' => 37]; ksort($ages); // Sort by name (key) print_r($ages); // Output: Array ( [Amy] => 37 [Joe] => 43 [Peter] => 35 ) ?>