添加 0015.三数之和 PHP版本

problems/0015.三数之和.md

@@ -393,6 +393,46 @@ function threeSum(array $nums): array
 }
 ```
 
+PHP:
+```php
+class Solution {
+    /**
+     * @param Integer[] $nums
+     * @return Integer[][]
+     */
+    function threeSum($nums) {
+        $res = [];
+        sort($nums);
+        for ($i = 0; $i < count($nums); $i++) {
+            if ($nums[$i] > 0) {
+                return $res;
+            }
+            if ($i > 0 && $nums[$i] == $nums[$i - 1]) {
+                continue;
+            }
+            $left = $i + 1;
+            $right = count($nums) - 1;
+            while ($left < $right) {
+                $sum = $nums[$i] + $nums[$left] + $nums[$right];
+                if ($sum < 0) {
+                    $left++;
+                }
+                else if ($sum > 0) {
+                    $right--;
+                }
+                else {
+                    $res[] = [$nums[$i], $nums[$left], $nums[$right]];
+                    while ($left < $right && $nums[$left] == $nums[$left + 1]) $left++;
+                    while ($left < $right && $nums[$right] == $nums[$right - 1]) $right--;
+                    $left++;
+                    $right--;
+                }
+            }
+        }
+        return $res;
+    }
+}
+```
 
 
 -----------------------