$re = '/http://myServer:28020/MyService/ItemWebService\.json\?action=keywordSearch(?:&?[^=&]*=[^=&]*)*/';
$str = 'http://myServer:28020/MyService/ItemWebService.json?action=keywordSearch&username=StockOnHandPortlet&sessionId=2H7Rr9kCWPgIZfrxQiDHKp0&keywords=blue&itemStatus=A';
preg_match($re, $str, $matches, PREG_OFFSET_CAPTURE, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php