diff --git a/wchat/common/Help.php b/wchat/common/Help.php
index 23bbab7..4528ead 100644
--- a/wchat/common/Help.php
+++ b/wchat/common/Help.php
@@ -36,17 +36,17 @@ class Help extends Miniprogarampage
 	 */
 	private static function xmlChild(array $array)
 	{
-		$= '';
+		$string = '';
 		foreach ($array as $key => $value) {
 			if (is_array($value)) {
-				$.= static::xmlChild($value);
+				$string .= static::xmlChild($value);
 				continue;
 			}
 
 			if (is_numeric($value)) {
-				$.= "<" . $key . ">" . $value . "</" . $key . ">";
+				$string .= "<" . $key . ">" . $value . "</" . $key . ">";
 			} else {
-				$.= "<" . $key . "><![CDATA[" . $value . "]]></" . $key . ">";
+				$string .= "<" . $key . "><![CDATA[" . $value . "]]></" . $key . ">";
 			}
 		}
 		return $string;
@@ -163,7 +163,7 @@ class Help extends Miniprogarampage
 	public static function sign(array $array, $key, $type)
 	{
 		ksort($array, SORT_ASC);
-		$= [];
+		$string = [];
 		foreach ($array as $hashKey => $val) {
 			if (empty($val)) {
 				continue;
@@ -171,7 +171,7 @@ class Help extends Miniprogarampage
 			$string[] = $hashKey . '=' . $val;
 		}
 		$string[] = 'key=' . $key;
-		$= implode('&', $string);
+		$string = implode('&', $string);
 		if ($type == 'MD5') {
 			return strtoupper(md5($string));
 		} else {