$re = '/[^\-+\*=]+\s*[\-+\*=]{1,2}\s*(\'[^\']+\')\s*\&\&/';
$str = 'mydate == \'one day ago\' && mydate > \'2014-05-16 16:00:00\'';
preg_match($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