$re = '/-\d+(\.\d*)*/';
$str = '<div style="color: red; display.: inline-block;"><i class="fa fa-arrow-down" aria-hidden="true"></i> -1%</div>';
preg_match_all($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