$re = '/Time in seconds =\s*([^\n]*)/m';
$str = 'Class = C
Size = 162x 162x 162
Iterations = 200
Time in seconds = 23.68
Total processes = 900
Compiled procs = 900
Mop/s total = 121032.40
Mop/s/process = 134.48';
preg_match_all($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