From 692f63a77e55a2b1141b4eac78634db306eb4ec9 Mon Sep 17 00:00:00 2001
From: alanx15a2 <alanx15a2@yahoo.com.tw>
Date: Thu, 30 May 2024 12:00:12 +0800
Subject: [PATCH] =?UTF-8?q?=E4=BA=8C=E5=8F=89=E6=A0=91=E7=9A=84=E9=80=92?=
 =?UTF-8?q?=E5=BD=92=E9=81=8D=E5=8E=86=20add=20php=20version?=
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---
 problems/二叉树的递归遍历.md | 56 ++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)

diff --git a/problems/二叉树的递归遍历.md b/problems/二叉树的递归遍历.md
index a1d49e98..f2a97f4d 100644
--- a/problems/二叉树的递归遍历.md
+++ b/problems/二叉树的递归遍历.md
@@ -671,6 +671,62 @@ public void Traversal(TreeNode cur, IList<int> res)
 }
 ```
 
+### PHP
+```php
+// 144.前序遍历
+function preorderTraversal($root) {
+    $output = [];
+    $this->traversal($root, $output);
+    return $output;
+}
+
+function traversal($root, array &$output) {
+    if ($root->val === null) {
+        return;
+    }
+
+    $output[] = $root->val;
+    $this->traversal($root->left, $output);
+    $this->traversal($root->right, $output);
+}
+```
+```php
+// 94.中序遍历
+function inorderTraversal($root) {
+    $output = [];
+    $this->traversal($root, $output);
+    return $output;
+}
+
+function traversal($root, array &$output) {
+    if ($root->val === null) {
+        return;
+    }
+
+    $this->traversal($root->left, $output);
+    $output[] = $root->val;
+    $this->traversal($root->right, $output);
+}
+```
+```php
+// 145.后序遍历
+function postorderTraversal($root) {
+    $output = [];
+    $this->traversal($root, $output);
+    return $output;
+}
+
+function traversal($root, array &$output) {
+    if ($root->val === null) {
+        return;
+    }
+
+    $this->traversal($root->left, $output);
+    $this->traversal($root->right, $output);
+    $output[] = $root->val;
+}
+```
+
 
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