Detailed usage of PHP set_error_handler ()

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

Set_error_handler This function is designed to prevent false path leaks

What is the wrong path leak?

We write programs that inevitably have problems (which are often problematic), and when PHP encounters an error, it gives the location of the error script, the number of rows, and the reason

A lot of people say it's not a big deal. Indeed, during the debugger phase, this is really nothing, and I think it is necessary to give the wrong path.

But the consequences of revealing the actual path are disastrous, and for some intruders, this information is very important, and in fact there are a lot of servers that are having this problem.

Some network management simply set the PHP configuration file display_errors to off to solve (it seems that we are doing this), but I think this method is too negative.

Sometimes, we really need PHP to return the wrong information for debugging. And in the case of errors may also need to give the user a confession, or even navigate to another page.

So, what's the solution?

PHP provides the function Set_error_handler () of the custom error handling handle starting from 4.1.0, but very few script writers know.

Set_error_handler is used as follows:

PHP code

1. String Set_error_handler (callback Error_Handler [, int error_types])

Now we are using 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 (can make this judgment by IP or login user ID)

PHP code

//admin is the administrator's identity, true for administrators.  The custom error handler must have these 4 input variables $errno, $errstr, $errfile, $errline, otherwise invalid. function My_error_handler ($errno, $errstr, $errfile, $errline) {//If not an administrator, filter the actual path if (!admin) {$ERRF          Ile=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 "program has stopped running, please contact the administrator.          ";          Exit script exit when error level errors are encountered;            Break          Case E_warning:echo "WARNING: [ID $errno] $errstr (line: $errline of $errfile) \ n";            Break      Default://Do not show error break at notice level; }  }

So you can customize an error handler, so how do you give the wrong handling to the custom function?

PHP code

Apply to Class  Set_error_handler (Array (& $this, "Apperror"));    The practice of the example  Set_error_handler ("My_error_handler");

So easy, this can be a good solution to the security and debugging convenience contradictions. And you can also take a little thought to make the error message more beautiful to match the style of the website.

The original author gave two points to pay attention to the place, I also let out, hope to arouse the attention of our compatriots:

1. E_error, E_parse, E_core_error, e_core_warning, E_compile_error, and e_compile_warning are not handled by this handle, which means they are displayed in the most primitive way. However, these errors are either compiled or the PHP kernel is faulty and will not normally occur.

2. After using Set_error_handler (), the error_reporting () will be invalidated. That is, all errors (except for the above errors) will be given to the custom function processing.

Finally, the original author gives an example (what a really serious and responsible good Man ha.) Oh

php Code

Define a function, define it in other files, and call function MyErrorHandler ($errno, $errstr, $errfile, $errline) with require () {//For security reasons, do not expose the true      Real physical path, the following two lines filter the actual path $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 ' t execute PHP Internal Error handler */return TRUE;  }  The following begins the connection to the MySQL server, we deliberately specify the MySQL port is 3333, the actual is 3306.  $link _id= @mysql_pconnect ("localhost:3333", "root", "password");  Set_error_handler (MyErrorHandler);      if (! $link _id) {trigger_error ("error", E_user_error); }

Well, according to the explanations above, and the original author's earnest and responsible attitude, I think if I don't learn this set_error_handler function, then I really should go to the wall.

Well, to summarize, here are three ways to use Set_error_handler:

PHP code

class callbackclass {function callbackfunction () {//refers to $this } function Staticfunction () {//doesn ' t refer to $this}} function Nonclassfunction ($errno, $err  STR, $errfile, $errline) {}//Three methods are as follows: 1:set_error_handler (' nonclassfunction '); Go directly to a normal function nonclassfunction 2:set_error_handler (Array (' Callbackclass ', ' staticfunction '));      Go to static method under Callbackclass class Staticfunction 3: $o =& new Callbackclass ();  Set_error_handler (Array ($o, ' callbackfunction '));    Going to the constructor of a class is essentially the same as the fourth one below.      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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