PHP: Reorder arrays after unset()

There are 2 functions involved.

1. Search array items for a given string
2. unset() array item if string not found

$array = array("first", "second", "third", "fourth");

foreach($array as $i=> $string) {  
 if(stristr($string, "e")) {  
    unset($array[$i]);
 }   

}

second is the array item with the character 'e'. If its unset, $array[1] would be left empty:

$array[0] = "first"  
$array[1] = ""  
$array[2] = "third"  
$array[3] = "fourth"

I want $array[1] to be removed from the array (like in array_shift()), so that third takes the place of second and fourth the place of third:

$array[0] = "first"    
$array[1] = "third"  
$array[2] = "fourth"