Flattening an Array

flatten_array.php

<?php
	$initialArray = [[1, 2, [3]], 4];
	/**
	 * This function is used to flatten arrays and also even nested arrays.
	 * 
	 * It first loops through each element of the array and if the element is an
	 * integer it adds it as an element of the flattened array (flat 1). Else if the
	 * element is an array, it passes the already flatened array to the function and then
	 * it flattens that array too (flat 2). It then assigns the new flattend array together
	 * with the already existing elements of the array to the flattened array (which contains 
	 * all the elements in flat 1 and flat 2). It does it till all nested arrays are flattened
	 * 
	 * @param  array  $array     
	 * @param  array  $flatArray 
	 * @return array
	 */
	function makeItFlat(array $array, array $flatArray = []) {
		foreach ($array as $element) {
			if (is_int($element)) {
				$flatArray[] = $element;
			} else if (is_array($element)) {
				$flatArray = makeItFlat($element, $flatArray);
			}
		}
		return $flatArray;
	}
	$finalArray = makeItFlat($initialArray);
	echo "<pre>"; 
	print_r($finalArray); 
	echo "</pre>";
?>