PHP关联数组如何实现根据元素值删除元素？

<?php 
$array1 = array("a" => "green", "red", "blue", "red"); 
$array2 = array("b" => "green"); 
$result = array_diff($array1, $array2);
//这样就相当于删除$array1里的值为"green"的元素。 
print_r($result); 
?>

function removeArrayElement(&$ar,$val)
{
$tmp = array();
foreach($ar as $k => $arc)
{
 if($arc!=$val)
 {
 $tmp[$k]=$arc;
 }
}
$ar = $tmp;
unset($tmp);
}