trigger_error

    (PHP 4 >= 4.0.1, PHP 5, PHP 7, PHP 8)

    trigger_error — Generates a user-level error/warning/notice message

    Description

    trigger_error(string $message, int $error_level = E_USER_NOTICE): true

    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

    message

    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_level

    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

    Always returns true.

    Errors/Exceptions

    This function throws a ValueError if error_level is not one of E_USER_ERROR, E_USER_WARNING, E_USER_NOTICE, E_USER_DEPRECATED.

    Changelog

    Version Description
    8.0.0 The function now throws a ValueError if an invalid error_level is specified. Previously, it returned false.

    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

    Warning

    HTML entities in message are not escaped. Use htmlentities() on the message if the error is to be displayed in a browser.

    See Also

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    User Contributed Notes 5 notes

    up
    54
    someone at attbi dot com
    21 years ago
    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');
    }
    up
    14
    Howard Yeend
    15 years ago
    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"
    up
    8
    richard at 2006 dot atterer dot net
    18 years ago
    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');
    up
    5
    aydin dot kn12 at gmail dot com
    10 years ago
    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...

    ?>
    up
    4
    PhpMyCoder
    14 years ago
    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!
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