添加0055.右旋字符串.md PHP版本

problems/kamacoder/0055.右旋字符串.md

@@ -336,6 +336,32 @@ var reverseLeftWords = function(s, n) {
 
 ### PHP：
 
+```php
+<?php
+// 反转函数
+function reverse(&$s, $start, $end) {
+    for ($i = $start, $j = $end; $i < $j; $i++, $j--) {
+        $tmp = $s[$i];
+        $s[$i] = $s[$j];
+        $s[$j] = $tmp;
+    }
+}
+    
+// 标准输入：读取右旋转位数和字符串    
+$n = trim(fgets(STDIN));
+$s = trim(fgets(STDIN));
+// 字符串长度
+$len = strlen($s);
+// 先部分反转
+reverse($s, $len - $n, $len - 1);
+reverse($s, 0, $len - $n - 1);
+// 再整体反转
+reverse($s, 0, $len - 1);
+
+echo $s;
+?>
+```
+
 
 ### Scala:
 
@@ -349,3 +375,4 @@ var reverseLeftWords = function(s, n) {
 <a href="https://programmercarl.com/other/kstar.html" target="_blank">
   <img src="../pics/网站星球宣传海报.jpg" width="1000"/>
 </a>
+