php - __autoload() vs include,will __autoload() output something? -

i developing programm , it's based on third-party.i write class , use __autoload() load class. program runs following:
1.i upload script remote server.
2.the third-party server request script param.
3.my script return str , third-party server check str,if str same param,it's valid,if not,it's not valid.
now,the problem is:
when use __autoload(),it raise error , when replace __autoload include/require run exactly.
code following:

wechat.class.php

        public function __construct($options){             $this->_token=isset($options['token'])?$options['token']:'';         }          public function test(){             var_dump($this->_token);         }          private function checksignature(){             $signature = isset($_get["signature"])?$_get["signature"]:'';             $timestamp = isset($_get["timestamp"])?$_get["timestamp"]:'';             $nonce = isset($_get["nonce"])?$_get["nonce"]:'';              $token = $this->_token;             $tmparr = array($token, $timestamp, $nonce);             sort($tmparr, sort_string);             $tmpstr = implode( $tmparr );             $tmpstr = sha1( $tmpstr );              if( $tmpstr == $signature ){                 return true;             }else{                 return false;             }         }          public function valid($return=false){             $echostr=isset($_get['echostr'])?$_get['echostr']:'';             if($return){                 if($echostr){                     if($this->checksignature()){                         return $echostr;                     }else{                         return false;                     }                 }else{                     return $this->checksignature();                 }             }else{                 if($echostr){                     if($this->checksignature()){                         die($echostr);                     }else{                         die('no access');                     }                 }else{                     if($this->checksignature()){                         return true;                     }else{                         die('no access');                     }                 }             }         }      } ?> 

wechat.php

<?php     function __autoload($classname){         include "./wechat/".$classname.".class.php";     }     $options=array(             'token'=>'tudouya',         );     $wechat=new wechat($options);     $wechat->valid(); ?> 

addition,my php version 5.4.i test script long , find both __autoload() , include work in php 5.2,but not in php 5.4.
think if there bugs in php,but can't decide.
hope describe question , sorry bad english.

the answer is:

include "./wechat/".strtolower($classname).".class.php"; 

it try include wechat.class.php otherwise (with uppercase w, not exist file.