perg_replace technique

/*
This is a useful technique for passing matched data into other
functions to be evaluated and replaced in parsed strings.

This example is simple. It rewrites the tag emulating being
passed thru a proxy.
*/

$html = file_get_contents('http://www.yahoo.com/');
print "$html

";
$attr= 'src';
$webroot='proxy';
$html=preg_replace('/(\s)?'.$attr.'="([^\s]*?)"/ei',
"make_new_img_tag('$attr','$2','$1','$webroot');",
$html);
print "";


function make_new_img_tag($attr, $filename, $prefix, $webroot) {
$b64val = base64_encode($filename);
return $prefix$attr.'="'.$webroot.'/browse/'.$b64val.'"';
}
?>