<?
    $array[0] = 'aap';
    $array[1] = 'noot';
    $array[3] = 'mies';
    $array[7] = 'wim';
    $array[8] = 'zus';
    $array[9] = 'jet';
    print_r($array);    // print the array
    echo '<br />';
    $size = count($array);  // 6 elements in array
    $r = 0; // read position
    $i = 0; // insert position
    while($i < $size){
        if(isset($array[$r])){  // if there is an element at read position
            $temp = $array[$r]; // read the value into a temp variable
            unset($array[$r]);  // unset (remove from array) the read value
            $array[$i] = $temp; // place it into the array at insert position
            $i++;   // increase inster position
        }
        $r++;   // increase read position
    }
    print_r($array);
?>