fix(php): 修复字符串偏移设置功能

- 移除了调试用的 var_dump 语句
- 在数组维度存储解析中正确管理 inAssignExpr 状态
- 修正测试文件中的测试名称描述

src/Php/CompilerBase.php

@@ -1081,7 +1081,6 @@ class CompilerBase extends \PhpAot\Core\Translator
             $var = $this->parsePropertyFetch($left, true);
         } elseif ($this->isArrayDimFetch($left)) {
             $tmp = $this->parseIdentifier($left->var);
-            var_dump($tmp);
             if ($this->isVarExpr($left->var) and $this->getVarType($tmp) === self::TYPE_STR) {
                 if ($left->dim === null) {
                     $this->fatalError($left, 'Cannot use [] for strings');
@@ -1720,7 +1719,10 @@ class CompilerBase extends \PhpAot\Core\Translator
 
     protected function parseArrayDimStore($array, $dim, $var): string
     {
+        $oriInAssignExpr = $this->inAssignExpr;
+        $this->inAssignExpr = true;
         $id = $this->parseIdentifier($array);
+        $this->inAssignExpr = $oriInAssignExpr;
 
         return $id . '.offsetSet(' . $this->trimBrackets($dim) . ', ' . $this->trimBrackets($var) . ')';
     }

tests/aot/str-offset-set.phpt

@@ -1,5 +1,5 @@
 --TEST--
-strlen
+string offset set
 --FILE--
 <?php
 $s1 = "hello world";