Merge pull request #1410 from fmtvar/1047

添加(1047.删除字符串中的所有相邻重复项.md)：php版本

problems/1047.删除字符串中的所有相邻重复项.md

@@ -374,6 +374,34 @@ func removeDuplicates(_ s: String) -> String {
     return String(stack)
 }
 ```
+
+
+PHP:
+```php
+class Solution {
+    function removeDuplicates($s) {
+        $stack = new SplStack();
+        for($i=0;$i<strlen($s);$i++){
+            if($stack->isEmpty() || $s[$i] != $stack->top()){
+                $stack->push($s[$i]);
+            }else{
+               $stack->pop(); 
+            }
+        }
+
+        $result = "";
+        while(!$stack->isEmpty()){
+            $result.= $stack->top();
+            $stack->pop();
+        }
+        
+        // 此时字符串需要反转一下
+        return strrev($result);
+    }
+}
+```
+
+
 Scala:
 ```scala
 object Solution {
@@ -396,5 +424,6 @@ object Solution {
   }
 }
 ```
+
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