check if file exists in php

Question

if (!(file_exists(http://mysite.com/images/thumbnail_1286954822.jpg))) {   
$filefound = \'0\';                         
}

why won\'t this work?

Answer 1

if (!file_exists('http://example.com/images/thumbnail_1286954822.jpg')) {   
$filefound = '0';
}