$re = '/tooltext=(.*?\\\\&)*.*?&/im';
$str = '\'&label=20:01:27&tooltext=abc\\&|\\|cba&value=6|59|58|89&color=ff0000|00ffff\'
\'&label=20:01:27&tooltext=abc\\&|\\|cba&value=6|59|58|89\'
\'&label=20:01:27&tooltext=abc&|\\|cba&value=6|59|58|89\'
\'&label=20:01:27&tooltext=abc\\&\\as&\\&dsa\\&|\\|cba&value=6|59|58|89\'';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($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