Preg match text php dont work

Preg match text php dont work

Hello I would like to use preg_match I have it, why don't work?
$source = "<span class=\"middle\">".
"<span class=\"play\"></span>".
"<img width=\"114\"
src=\"http://i.ytimg.com/vi/PnmEKNi1DtY/default.jpg\" alt=\"\"></span>
1";
preg_match("'<span class=\"middle\"><span class=\"play\"></span> <img
width=\"114\" src=\"http://i.ytimg.com/vi/(.*?)/default.jpg\"
alt=\"\"></span> 1'si", $source, $match);
foreach($match[1] as $val)
{
echo $val."<br>";
}
Outputs:
Warning: Invalid argument supplied for foreach()