flattenarray.php

<?php
/**
 * Expects a multi-dimensional array and returns a flattened array contianing the values.
 *
 * @param array $array A multi-dimensional array.
 * @return array 
 */
function flatten_array($array) {
  $flatArray = [];
  foreach ($array as $item) {
     if (is_array($item)) {
       $flatArray = array_merge( $flatArray, flatten_array($item) );
     } else {
       $flatArray[] = $item;
     }
  }
  return $flatArray;
}

// $test1 = [1,2,3];
// $test2 = [1,2,[3]];
// $test3 = [1,2,[3, [4, 5, [6]]]];
// foreach ([$test1, $test2, $test3] as $test) {
// 	echo print_r( flatten_array($test), true );
// }