Detailed usage of php set_error_handler()

This article shares with you the detailed usage of php set_error_handler(), which has a certain reference value. Friends in need can refer to it

Reprinted: http://us.php.net/manual/en/function.set-error-handler.php

set_error_handler function The function is to prevent wrong path leakage

What is wrong path leakage?

When we write programs, there will inevitably be problems (problems are often encountered ), and when PHP encounters an error, it will give the location, line number and reason of the error script

Many people say that this is not a big deal. Indeed, in the debugging phase, this really doesn't matter, and I think giving the error path is necessary.

But the consequences of leaking the actual path are unimaginable. For some intruders, this information is very important. In fact, many servers now have this problem.

Some network administrators simply set the display_errors in the PHP configuration file to Off to solve the problem (it seems like we did this), but I think this method is too negative.

Sometimes, we really need PHP to return error information for debugging. And when something goes wrong, you may also need to give the user an explanation or even navigate to another page.

So, what’s the solution?

PHP has provided the function set_error_handler() for custom error handling handles since 4.1.0, but few script writers know it.

The method of using set_error_handler is as follows:

##Php code

string set_error_handler ( callback error_handler [, int error_types])

Now we use custom error handling to filter out the actual path.

For example: Suppose there is a variable $admin, we are used to determine whether the visitor is an administrator (this determination can be made by IP or logged in user ID)

##Php code

//admin为管理员的身份判定，true为管理员。  
//自定义的错误处理函数一定要有这４个输入变量$errno,$errstr,$errfile,$errline，否则无效。  
function my_error_handler($errno,$errstr,$errfile,$errline)  
{  
    //如果不是管理员就过滤实际路径  
    if(!admin)  
    {  
        $errfile=str_replace(getcwd(),"",$errfile);  
        $errstr=str_replace(getcwd(),"",$errstr);  
    }  
    switch($errno)  
    {  
        case E_ERROR:  
        echo "ERROR: [ID $errno] $errstr (Line: $errline of $errfile) \n";  
        echo "程序已经停止运行，请联系管理员。";  
        //遇到Error级错误时退出脚本  
        exit;  
        break;  
  
        case E_WARNING:  
        echo "WARNING: [ID $errno] $errstr (Line: $errline of $errfile) \n";  
        break;  
  
        default:  
        //不显示Notice级的错误  
        break;  
    }  
}

In this way, an error handling function is customized, so how to hand over error processing to this custom function?

Php code

// 应用到类  
set_error_handler(array(&$this,"appError"));  
  
//示例的做法  
set_error_handler("my_error_handler");

so easy，这样，就可以很好地解决安全和调试方便的矛盾了。而且你还可以花点心思，使错误提示更加美观以配合网站的风格。

原作者给出了两点需要注意的地方，我也放出来吧，希望引起广大同胞们的注意：

1. E_ERROR、E_PARSE、E_CORE_ERROR、E_CORE_WARNING、 E_COMPILE_ERROR、E_COMPILE_WARNING是不会被这个句柄处理的，也就是会用最原始的方式显示出来。不过出现这些错误都是编 译或PHP内核出错，在通常情况下不会发生。

2. 使用set_error_handler()后，error_reporting ()将会失效。也就是所有的错误（除上述的错误）都会交给自定义的函数处理。

最后，原作者又给出了一个示例（真是个认真负责的好人哈。呵呵）

Php代码

//先定义一个函数，也可以定义在其他的文件中，再用require()调用  
function myErrorHandler($errno, $errstr, $errfile, $errline)  
{  
　　　　　//为了安全起见，不暴露出真实物理路径，下面两行过滤实际路径  
    $errfile=str_replace(getcwd(),"",$errfile);  
    $errstr=str_replace(getcwd(),"",$errstr);  
  
    switch ($errno) {  
    case E_USER_ERROR:  
  
     echo "<b>My ERROR</b> [$errno] $errstr<br />\n";  
        echo "  Fatal error on line $errline in file $errfile";  
        echo ", PHP " . PHP_VERSION . " (" . PHP_OS . ")<br />\n";  
        echo "Aborting...<br />\n";  
        exit(1);  
        break;  
  
    case E_USER_WARNING:  
        echo "<b>My WARNING</b> [$errno] $errstr<br />\n";  
        break;  
  
    case E_USER_NOTICE:  
        echo "<b>My NOTICE</b> [$errno] $errstr<br />\n";  
        break;  
  
    default:  
        echo "Unknown error type: [$errno] $errstr<br />\n";  
        break;  
    }  
  
    /* Don&#39;t execute PHP internal error handler */  
    return true;  
}  
  
//下面开始连接MYSQL服务器，我们故意指定MYSQL端口为3333,实际为3306。  
$link_id=@mysql_pconnect("localhost:3333","root","password");  
set_error_handler(myErrorHandler);  
if (!$link_id) {  
    trigger_error("出错了", E_USER_ERROR);  
    }

嗯，根据上面的那些解释，以及原作者认真负责的态度，我想如果我还学不会这个set_error_handler函数，那么我真该去撞墙了。

好了，总结一下，下面是 set_error_handler 三种用法：

Php代码

class CallbackClass {  
   function CallbackFunction() {  
       // refers to $this  
   }  
  
   function StaticFunction() {  
       // doesn't refer to $this  
   }  
}  
  
function NonClassFunction($errno, $errstr, $errfile, $errline) {  
}  
  
// 三种方法如下:  
  
1: set_error_handler('NonClassFunction');  // 直接转到一个普通的函数 NonClassFunction  
  
2: set_error_handler(array('CallbackClass', 'StaticFunction')); // 转到 CallbackClass 类下的静方法 StaticFunction  
  
3: $o =& new CallbackClass();  
    set_error_handler(array($o, 'CallbackFunction'));  // 转到类的构造函数，其实本质上跟下面的第四条一样。  
  
4. $o = new CallbackClass();  
  
  
// The following may also prove useful:  
  
class CallbackClass {  
   function CallbackClass() {  
       set_error_handler(array(&$this, 'CallbackFunction')); // the & is important  
   }  
     
   function CallbackFunction() {  
       // refers to $this  
   }  
}

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