$re = '/(\d+д)?(\d+ч)?(\d+м)?(\d+с)?/i';
$str = ' 25д10ч3м10с
25д0ч3м10с
15м30с
10д5с
10ч
15м
30с
25д3м11с';
$subst = "";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
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