feat: add php solution to lc problem: No.1323 (doocs#989)

Author: Qiu-IT

solution/1300-1399/1323.Maximum 69 Number/README.md

@@ -152,6 +152,23 @@ int maximum69Number(int num) {
 }
 ```
 
+### **PHP**
+
+```php
+class Solution {
+    /**
+     * @param Integer $num
+     * @return Integer
+     */
+    function maximum69Number($num) {
+        $num = strval($num);
+        $n = strpos($num, "6");
+        $num[$n] = 9;
+        return intval($num);
+    }
+}
+```
+
 ### **...**
 
 ```

solution/1300-1399/1323.Maximum 69 Number/README_EN.md

@@ -139,6 +139,23 @@ int maximum69Number(int num) {
 }
 ```
 
+### **PHP**
+
+```php
+class Solution {
+    /**
+     * @param Integer $num
+     * @return Integer
+     */
+    function maximum69Number($num) {
+        $num = strval($num);
+        $n = strpos($num, "6");
+        $num[$n] = 9;
+        return intval($num);
+    }
+}
+```
+
 ### **...**
 
 ```

solution/1300-1399/1323.Maximum 69 Number/Solution.php

@@ -0,0 +1,12 @@
+class Solution {
+    /**
+     * @param Integer $num
+     * @return Integer
+     */
+    function maximum69Number($num) {
+        $num = strval($num);
+        $n = strpos($num, "6");
+        $num[$n] = 9;
+        return intval($num);
+    }
+}