Search string using an array of values

[gosman]

I have the following code

$string="red and blue are primary colors";
$colors=array('red','green','blue');
$colorvalue=array();

I want to acheive the following.

1. Search the $string to find any occurrence of the values in the $colors array

2. when a match is found populate the $colorvalue array with the color key.

So using the above example I would have the following result

$colorvalue=array(0,2);

Any help really appreciated.

[Anyango]

<?
$string="red and blue are primary colors"; 
$colors=array('red','green','blue'); 
$colorvalue=array(); 

$i=0;
foreach($colors as $color)
{
 if(strpos($string,$color)!==false)
 {
 $colorvalue[]=$i;
 }
 $i++;
}

print_r($colorvalue);
?>

[gosman]

Thank you Anyango works great.