$re = '/[$]this->translate[(]\'((?:[^\'\\\\]|\\\\.|\'\')*)\'[)];/mix';
$str = '$This->Translate(\'(?:Droids\\\');{2}\');
$NotTranalate(\'fdasad\');
$this->translate(\'[a-zA-Z]\');
$this->translate(\'1_category_label\');
';
$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