PHP array_flatten() function. Convert a multi-dimensional array into a single-dimensional array.

array_flatten.php

<?php function array_flatten($array, $prefix = '') {     
$result = array();     
foreach($array as $key=>$value) {
        if(is_array($value)) {
            $result = $result + array_flatten($value, $prefix . $key . '.');
        }
        else {
            $result[$prefix.$key] = $value;
        }
    }
    return $result;
}

<?php 

/**
 * Convert a multi-dimensional array into a single-dimensional array.
 * @param  array $array The multi-dimensional array.
 * @return array
 */
function array_flatten($array) { 
  if (!is_array($array)) { 
    return false; 
  } 
  $result = array(); 
  foreach ($array as $key => $value) { 
    if (is_array($value)) { 
      $result = array_merge($result, array_flatten($value)); 
    } else { 
      $result[$key] = $value; 
    } 
  } 
  return $result; 
}





Using Standard PHP Library
$itcArray = array('a', 'b', array('c','d', array('e', 'f', 'g'), 'h'), 'i');
$itcIterate = new RecursiveIteratorIterator(new RecursiveArrayIterator($itcArray));
 
foreach($itcIterate as $result) {
  echo $result. " ";
}

Using array_walk_recursive
        function flatten(array $array) {
    $return = array();
    array_walk_recursive($array, function($a) use (&$return) { $return[] = $a; });
    return $return;
}
 
$itcArray = array('a', 'b', array('c','d', array('e', 'f', 'g'), 'h'), 'i');
$result = flatten($itcArray);
 
echo "<pre>";
print_r($result);
echo "</pre>";

Using Stack
        
        function flatten(array $array) {
    $flat = array(); // initialize an array
    $stack = array_values($array); // initialize stack
    while($stack) { // process the stack until finish
        $value = array_shift($stack);
        if (is_array($value)) { // a value to further process
            $stack = array_merge(array_values($value), $stack);
        }
        else { // a value to take
           if(!empty($value)) {
	       $flat[] = $value
           }	
        }
    }
    return $flat;
}
 
$itcArray = array('a', 'b', array('c','d', array('e', 'f', 'g'), 'h'), 'i');
$result = flatten($itcArray);
 
echo "<pre>";
print_r($result);
echo "</pre>";