$re = '/[[^\[{1}(?![[:digit:]]\){1}/m';
$str = '-0.2122,-0.1213
-0.2750,-0.2122
-0.1213,-0.0222
-0.1213,-0.0222';
preg_match_all($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