trigger_error

PhpMyCoder (2010-07-15 03:18:07)

For those of you looking to use your own file or line number in the error (possibly using debug_backtrace()) instead of the ones created by trigger_error(), here is a solution:
Create a custom function to handle E_USER_ERRORs that simply outputs the error type and message, while excluding the line number and file trigger_error() reports. You may also configure it to handle user warnings and notices if necessary (I did in the example below).

<?php
function error_handler($level, $message, $file, $line, $context) {
    //Handle user errors, warnings, and notices ourself
    if($level === E_USER_ERROR || $level === E_USER_WARNING || $level === E_USER_NOTICE) {
        echo '<strong>Error:</strong> '.$message;
        return(true); //And prevent the PHP error handler from continuing
    }
    return(false); //Otherwise, use PHP's error handler
}

function trigger_my_error($message, $level) {
    //Get the caller of the calling function and details about it
    $callee = next(debug_backtrace());
    //Trigger appropriate error
    trigger_error($message.' in <strong>'.$callee['file'].'</strong> on line <strong>'.$callee['line'].'</strong>', $level);
}

//Use our custom handler
set_error_handler('error_handler');

//-------------------------------
//Demo usage:
//-------------------------------
function abc($str) {
    if(!is_string($str)) {
        trigger_my_error('abc() expects parameter 1 to be a string', E_USER_ERROR);
    }
}

abc('Hello world!'); //Works
abc(18); //Error: abc() expects parameter 1 to be a string in [FILE].php on line 31
?>

This is a pretty simple concept and I'm sure most of you know this, but for those that don't, let it serve as a good example!

tudor AT iccblue DOT com DOT nospam (2009-10-15 08:07:02)

It actually turns out - at least on PHP 5.2.6 on XAMPP (Windows) that for the custom error handler, you will need to set $errorType as the first parameter, and only the second parameter as $message, i.e. in reverse order compared to how the manual states it now.

Howard Yeend (2009-07-05 04:39:59)

trigger_error always reports the line and file that trigger_error was called on. Which isn't very useful.

eg:

main.php:
<?php
include('functions.php');
$x = 'test';
doFunction($x);
?>

functions.php:
<?php
function doFunction($var) {
if(is_numeric($var)) {
 /* do some stuff*/
} else {
 trigger_error('var must be numeric');
}
}
?>

will output "Notice: var must be numeric in functions.php on line 6"
whereas "Notice: var must be numeric in main.php on line 4" would be more useful

here's a function to do that:

<?php

function error($message, $level=E_USER_NOTICE) {
$caller = next(debug_backtrace());
trigger_error($message.' in <strong>'.$caller['function'].'</strong> called from <strong>'.$caller['file'].'</strong> on line <strong>'.$caller['line'].'</strong>'."\n<br />error handler", $level);
}
?>

So now in our example:

main.php:
<?php
include('functions.php');
$x = 'test';
doFunction($x);
?>

functions.php:
<?php
function doFunction($var) {
    if(is_numeric($var)) {
         /* do some stuff*/
    } else {
         error('var must be numeric');
    }
}

function error($message, $level=E_USER_NOTICE) {
    $caller = next(debug_backtrace());
    trigger_error($message.' in <strong>'.$caller['function'].'</strong> called from <strong>'.$caller['file'].'</strong> on line <strong>'.$caller['line'].'</strong>'."\n<br />error handler", $level);
}
?>

now outputs:

"Notice: var must be numeric in doFunction called from main.php on line 4"

http://www.puremango.co.uk

webmaster at paramiliar dot com (2008-01-03 23:11:31)

We wanted to be able to pass an SQL query to the error handler on our site so we could monitor SQL problems, you cant do this through normal methods so we came up with this bridge script that 100% works

<?php

function myErrorHandler($errno, $errstr, $errfile, $errline){
    switch ($errno) {
    case E_USER_ERROR:
        if ($errstr == "(SQL)"){
            // handling an sql error
            echo "<b>SQL Error</b> [$errno] " . SQLMESSAGE . "<br />\n";
            echo "Query : " . SQLQUERY . "<br />\n";
            echo "On line " . SQLERRORLINE . " in file " . SQLERRORFILE . " ";
            echo ", PHP " . PHP_VERSION . " (" . PHP_OS . ")<br />\n";
            echo "Aborting...<br />\n";
        } else {
            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:
    case E_USER_NOTICE:
    }
    /* Don't execute PHP internal error handler */
    return true;
}

// function to test the error handling

function sqlerrorhandler($ERROR, $QUERY, $PHPFILE, $LINE){
    define("SQLQUERY", $QUERY);
    define("SQLMESSAGE", $ERROR);
    define("SQLERRORLINE", $LINE);
    define("SQLERRORFILE", $PHPFILE);
    trigger_error("(SQL)", E_USER_ERROR);
}

set_error_handler("myErrorHandler");

// trigger an sql error
$query = "SELECT * FROM tbl LIMIT 1";
$sql = @mysql_query($query)
    or sqlerrorhandler("(".mysql_errno().") ".mysql_error(), $query, $_SERVER['PHP_SELF'], __LINE__);
    

?>

richard at 2006 dot atterer dot net (2006-04-03 09:28:24)

Beware, trigger_error() is absolutely useless for transporting your own function's error messages in $php_errormsg:
ini_set('track_errors', TRUE);
function x() { trigger_error('MY ERROR'); }
@x();
echo "Error 1: \\"$php_errormsg\\"\\n";
@file_get_contents('/nonexisting');
echo "Error 2: \\"$php_errormsg\\"\\n";
This outputs:
Error 1: ""
Error 2: "failed to open stream: No such file or directory"
This behaviour is consistent with the description of $php_errormsg, which says that the variable will only be available within the scope in which the error occurred. The problem can be worked around with a custom error handler like the one below. However, I'm undecided whether changing the language in this way is good:
function errHandler($errno, $errstr, $errfile, $errline) {
global $php_errormsg; $php_errormsg = $errstr;
}
set_error_handler('errHandler');

mano at easymail dot hu (2005-04-26 05:13:24)

I am not so familiar with this but I think you can reach some of the functionality of try..catch with this function. I would disagree or correct the previous note. The @ is not the catch, it sets the error_reporting to 0 tempolary but with set_error_handler you can try to imitate some behavior like catch.
I've just made this to try if it possible, I never tried in projects but I think could work in php 4. Actually if you want to have the Trace of the error you need to use php4.3+.
Maybe not many of you will create new scripts in php4 and try to have some features from php5 but in some cases (extending older projects) this could be better error handling.

If this is a wrong approach, waiting for comments, if its not, use it!

<?
function catch($errno, $errstr, $errfile, $errline){
    $GLOBALS['throw'] = $errstr;
    $GLOBALS['throw_info'] = array(
        'Message'=>$errstr
        ,'Code'=>$errno
        ,'Line'=>$errline
        ,'File'=>$errfile
        ,'Trace'=>debug_backtrace()
    );
    
}
set_error_handler('catch');

function badgirl(){
    if(true){ //error occure
        trigger_error("BadGirlWithError",E_USER_NOTICE); // as throw with notice
        return; // ...because trigger_error does not stop the function
    }else{
       return true;
    }
}

// Try 
$GLOBALS['throw'] = null; // ...try...
$sheis = badgirl(); //could be @badgirl, display_errors is something else, this just the handling
// ..try
if($GLOBALS['throw']){  // This actually catch re-throws too...
    switch($GLOBALS['throw']){ // Catch
        case 'GoodGirlException':
            die('No bad girl today!');
        break;
        case 'BadGirlWithError':
            die('Bad girl has some error');
        break;
        default:
            return; // or you can make another trigger_error and re-throw another 'exception' or some other action
    }
}
echo "You will never see this line - @ only supress message, not a control flow";
echo "Wrong! You could see this:)";

?>

.mano

dzn'tM@ter (2004-01-20 09:05:23)

Some might think that trigger_error is like a throw() or an err.raise construction, and @ works like catch(){} one - in fact it's NOT.
function badgirl(){
trigger_error("shame on me",E_USER_ERROR);
return true;
}
$sheis = @badgirl();
echo "You will never see this line - @ only supress message, not a control flow";

robert at klugher dot com (2003-09-23 17:12:58)

This one took me some time ...
When you use trigger_error with your own error handler, the class instances are destroyed (don't know how to say it better, I am not an expert).
So, if you try to call a class function from within the error handler function, you will get 'Call to a member function on a non-object' error, even if this function works perfectly in the rest of your script.
Solution : re-use the xxx = new yyy to re-create the instance in the beginning of your error handler ... and then you can call the class functions you want !

mail at dooley dot cjb dot net (2003-07-29 19:16:53)

i recently began using a custom error handling class. the biggest problem is that, with call time pass by reference deprecated, you can't manipulate the error handler class after assigning at as the error handler (and it appears not to be returned by the set_error_handler method as the old error handler). my goal was to be able to store up all my non-fatal errors and print them at the end of script execution. that way i can use 'trigger_error' (which i actually have wrapped in a static method ErrorHandler::throwException for portability purposes... which is a pain because it always has the same line number information!!) for all kinds of errors, including user input erros. so when i check a user's password, for instance i would trigger a warning that said 'incorrect password'. of course i would only want this to print out the error once the script had completed.
so in my error handler class i have the following in the constructor:
function ErrorHandler()
{
$this->error_messages = array();
error_reporting (E_ALL);
set_error_handler(array($this,"assignError"));
}
and my assignError method:
//accept the required arguments
function assignError($errno, $errstr, $errfile, $errline)
{
//get the error string
$error_message = $errstr;
//if in debug mode, add line number and file info
if(ErrorHandler::DEBUG())
$error_message .= "<br>".basename($errfile).",line: ".$errline;
switch ($errno)
{
//if the error was fatal, then add the error
//display an error page and exit
case ErrorHandler::FATAL():
$this->setType('Fatal');
$this->addError($error_message);
Display::errorPage($this->errorMessages());
exit(1);
break;
//if it was an error message, add a message of
//type error
case ErrorHandler::ERROR():
$this->setType('Error');
$this->addError($error_message);
break;
//if it was a warning, add a message of type
//warning
case ErrorHandler::WARNING():
$this->setType('Warning');
$this->addError($error_message);
break;
//if it was some other code then display all
//the error messages that were added
default:
Display::errorRows($this->errorMessages());
break;
}
//return a value so that the script will continue
//execution
return 1;
}
the key part there is the 'default' behaviour. i found that if i call trigger_error with anything other than E_USER_ERROR, E_USER_WARNING or E_USER_NOTICE, then error code '2' is passed to the handler method. so when it is time to print all my non-fatal errors, like 'password and confirm password don't match' or something, i call ErrorHandler::printAllErrors()
function printAllErrors()
{
trigger_error("",2);
}
which leads to the default behaviour in my switch statement in the assignError method above. the only problem with this is that the weird bug 'Problem with method call' that occurs with some static method calls (that one person on the bug lists said was fixed and another said wouldn't be fixed until version 5) also produces error code 2!! i have just taken to suppressing these errors with @, because despite the alledged problem with the method call, the script still seems to execute fine.
iain.

someone at attbi dot com (2003-05-23 09:24:47)

sl0th, the idea is never to give out file names, line numbers, and cryptic codes to the user. Use trigger_error() after you used set_error_handler() to register your own callback function which either logs or emails the error codes to you, and echo a simple friendly message to the user.
And turn on a more verbose error handler function when you need to debug your scripts. In my init.php scripts I always have:
if (_DEBUG_) {
set_error_handler ('debug_error_handler');
}
else {
set_error_handler ('nice_error_handler');
}

sl0th at r00thell dot ath dot cx (2003-05-20 19:25:08)

Well this is a good way on debuging your php scripts, but i wouldn't feel
too comfortable by giving out my web servers structure.
Notice that what helps you finding and isolating errors in your php helps also a potential attacker.
Or maybe i am just paranoid, but its worth mention it.

ceo at l-i-e dot com (2002-10-28 17:20:56)

You should be using set_error_handler (possibly in conjuction with error_log and/or trigger_error) if you want FILE and LINE number information.
You don't need macros for this.

jason at lehighweb dot com (2001-07-16 00:28:25)

Fatal error: Cannot divide by zero in 
/home/phpwebmaster/public_html/test2.php on line 11

That almost looks evil, doesn't it?  Except that I made PHP print that out.

You see, most of use apply echo() style error checking in PHP, when in fact we could be using the trigger_error() function.

For example:

<?php
$divisor =;
if (assert ($divisor =0))
   trigger_error ("Cannot divide by zero", E_USER_ERROR);
?>

That will print out a PHP like error, making it easy to find errors in your logic.  It will print out the page, and the line number that the trigger_error() function is called on.  A handly little tool in debugging, as well as controlling error messages.  It also looks much more
prefossional than

echo "Cannot divide by zero"

Happy coding!

Note: This was taken directy from the PHP Newsletter located here: http://www.newbienetwork.net