feat: add php solution to lc problem: No.2404 (doocs#1003)

Author: Qiu-IT

solution/2400-2499/2404.Most Frequent Even Element/README.md

@@ -187,6 +187,30 @@ impl Solution {
 }
 ```
 
+### **PHP**
+
+```php
+class Solution {
+    /**
+     * @param Integer[] $nums
+     * @return Integer
+     */
+    function mostFrequentEven($nums) {
+        $max = $rs = -1;
+        for ($i = 0; $i < count($nums); $i++) {
+            if ($nums[$i] % 2 == 0) {
+                $hashtable[$nums[$i]] += 1;
+                if ($hashtable[$nums[$i]] > $max || ($hashtable[$nums[$i]] == $max && $rs > $nums[$i])) {
+                    $max = $hashtable[$nums[$i]];
+                    $rs = $nums[$i];
+                }
+            }
+        }
+        return $rs;
+    }
+}
+```
+
 ### **...**
 
 ```

solution/2400-2499/2404.Most Frequent Even Element/README_EN.md

@@ -174,6 +174,30 @@ impl Solution {
 }
 ```
 
+### **PHP**
+
+```php
+class Solution {
+    /**
+     * @param Integer[] $nums
+     * @return Integer
+     */
+    function mostFrequentEven($nums) {
+        $max = $rs = -1;
+        for ($i = 0; $i < count($nums); $i++) {
+            if ($nums[$i] % 2 == 0) {
+                $hashtable[$nums[$i]] += 1;
+                if ($hashtable[$nums[$i]] > $max || ($hashtable[$nums[$i]] == $max && $rs > $nums[$i])) {
+                    $max = $hashtable[$nums[$i]];
+                    $rs = $nums[$i];
+                }
+            }
+        }
+        return $rs;
+    }
+}
+```
+
 ### **...**
 
 ```

solution/2400-2499/2404.Most Frequent Even Element/Solution.php

@@ -0,0 +1,19 @@
+class Solution {
+    /**
+     * @param Integer[] $nums
+     * @return Integer
+     */
+    function mostFrequentEven($nums) {
+        $max = $rs = -1;
+        for ($i = 0; $i < count($nums); $i++) {
+            if ($nums[$i] % 2 == 0) {
+                $hashtable[$nums[$i]] += 1;
+                if ($hashtable[$nums[$i]] > $max || ($hashtable[$nums[$i]] == $max && $rs > $nums[$i])) {
+                    $max = $hashtable[$nums[$i]];
+                    $rs = $nums[$i];
+                }
+            }
+        }
+        return $rs;
+    }
+}