$re = '/At_[-0-9.]*_displacement/';
$str = 'At_5.2000_displacement
At_-6.4000_displacement
At_-0.4000_displacement
At_0.4000_displacement
At_2nd_-4.3000_displacement
At_2nd_2.2000_displacement';
preg_match_all($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