<?php

function __unshift(&$array, $value){
    $key = array_search($value, $array);
    if($key) unset($array[$key]);
    array_unshift($array, $value);  
    return $array;
}

$a = array("Apple", "Orange", "Banana", "Melon");
__unshift($a, "Melon");
__unshift($a, "Orange");
print_r($a);

?>