How can I get useful error messages in PHP?

The following enables all errors:

ini_set('display_startup_errors', 1);
ini_set('display_errors', 1);
error_reporting(-1);

Also see the following links

• http://php.net/manual/en/errorfunc.configuration.php#ini.display-errors
• http://php.net/manual/en/errorfunc.configuration.php#ini.display-startup-errors
• http://php.net/manual/en/function.error-reporting.php

The following code should display all errors:

<?php

// ----------------------------------------------------------------------------------------------------
// - Display Errors
// ----------------------------------------------------------------------------------------------------
ini_set('display_errors', 'On');
ini_set('html_errors', 0);

// ----------------------------------------------------------------------------------------------------
// - Error Reporting
// ----------------------------------------------------------------------------------------------------
error_reporting(-1);

// ----------------------------------------------------------------------------------------------------
// - Shutdown Handler
// ----------------------------------------------------------------------------------------------------
function ShutdownHandler()
{
    if(@is_array($error = @error_get_last()))
    {
        return(@call_user_func_array('ErrorHandler', $error));
    };

    return(TRUE);
};

register_shutdown_function('ShutdownHandler');

// ----------------------------------------------------------------------------------------------------
// - Error Handler
// ----------------------------------------------------------------------------------------------------
function ErrorHandler($type, $message, $file, $line)
{
    $_ERRORS = Array(
        0x0001 => 'E_ERROR',
        0x0002 => 'E_WARNING',
        0x0004 => 'E_PARSE',
        0x0008 => 'E_NOTICE',
        0x0010 => 'E_CORE_ERROR',
        0x0020 => 'E_CORE_WARNING',
        0x0040 => 'E_COMPILE_ERROR',
        0x0080 => 'E_COMPILE_WARNING',
        0x0100 => 'E_USER_ERROR',
        0x0200 => 'E_USER_WARNING',
        0x0400 => 'E_USER_NOTICE',
        0x0800 => 'E_STRICT',
        0x1000 => 'E_RECOVERABLE_ERROR',
        0x2000 => 'E_DEPRECATED',
        0x4000 => 'E_USER_DEPRECATED'
    );

    if(!@is_string($name = @array_search($type, @array_flip($_ERRORS))))
    {
        $name = 'E_UNKNOWN';
    };

    return(print(@sprintf("%s Error in file \xBB%s\xAB at line %d: %s\n", $name, @basename($file), $line, $message)));
};

$old_error_handler = set_error_handler("ErrorHandler");

// other php code

?>

The only way to generate a blank page with this code is when you have a error in the shutdown handler. I copied and pasted this from my own cms without testing it, but I am sure it works.

For syntax errors, you need to enable error display in the php.ini. By default these are turned off because you don't want a "customer" seeing the error messages. Check this page in the PHP documentation for information on the 2 directives: error_reporting and display_errors. display_errors is probably the one you want to change. If you can't modify the php.ini, you can also add the following lines to an .htaccess file:

php_flag  display_errors        on
php_value error_reporting       2039

You may want to consider using the value of E_ALL (as mentioned by Gumbo) for your version of PHP for error_reporting to get all of the errors. more info

3 other items: (1) You can check the error log file as it will have all of the errors (unless logging has been disabled). (2) Adding the following 2 lines will help you debug errors that are not syntax errors:

error_reporting(-1);
ini_set('display_errors', 'On');

(3) Another option is to use an editor that checks for errors when you type, such as PhpEd. PhpEd also comes with a debugger which can provide more detailed information. (The PhpEd debugger is very similar to xdebug and integrates directly into the editor so you use 1 program to do everything.)

Cartman's link is also very good: http://www.ibm.com/developerworks/library/os-debug/