trigger_error
(PHP 4 >= 4.0.1, PHP 5)
trigger_error — Generates a user-level error/warning/notice message
Description
$error_msg
[, int $error_type = E_USER_NOTICE
] )Used to trigger a user error condition, it can be used in conjunction with the built-in error handler, or with a user defined function that has been set as the new error handler (set_error_handler()).
This function is useful when you need to generate a particular response to an exception at runtime.
Parameters
-
error_msg -
The designated error message for this error. It's limited to 1024 bytes in length. Any additional characters beyond 1024 bytes will be truncated.
-
error_type -
The designated error type for this error. It only works with the E_USER family of constants, and will default to
E_USER_NOTICE.
Return Values
This function returns FALSE if wrong error_type is
specified, TRUE otherwise.
Examples
Example #1 trigger_error() example
See set_error_handler() for a more extensive example.
<?php
if ($divisor == 0) {
trigger_error("Cannot divide by zero", E_USER_ERROR);
}
?>
Notes
HTML entities in error_msg are not
escaped. Use htmlentities() on the message if
the error is to be displayed in a browser.
See Also
- error_reporting() - Sets which PHP errors are reported
- set_error_handler() - Sets a user-defined error handler function
- restore_error_handler() - Restores the previous error handler function
- The error level constants
Коментарии
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');
}
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');
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", $level);
}
?>
now outputs:
"Notice: var must be numeric in doFunction called from main.php on line 4"
For those of you looking to use your own file or line number in the error (possibly using debug_backtrace()) instead of the ones created by trigger_error(), here is a solution:
Create a custom function to handle E_USER_ERRORs that simply outputs the error type and message, while excluding the line number and file trigger_error() reports. You may also configure it to handle user warnings and notices if necessary (I did in the example below).
<?php
function error_handler($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!
If error_type is E_USER_ERROR then trigger_error throw FATAL ERROR and script stopped after this line.
<?php
$msg = 'This is the test message for echo';
trigger_error('Error message', E_USER_ERROR); // Script stopped after this line...
echo $msg; // This line does not appear...
?>