PHP: array keys search for insensitive input

array_keys_i.php

function array_keys_i($array, $str){ 
		$results = array();

	    foreach($array as $key => $value) { 
	        if(stristr($str,$value)) {
	        	$results[] = $key;
	        }
	    } 
		
		if(empty($results)) {
			return false;
		} else {
			return $results;	
		}
	}