How to get useful error messages in PHP?

 

I find programming in PHP quite frustrating. Quite often I will try and run the script and just get a blank screen back. No error message, just empty screen. The cause might have been a simple syntax error (wrong bracket, missing semicolon), or a failed function call, or something else entirely.

It is very difficult to figure out what went wrong. I end up commenting out code, entering "echo" statements everywhere, etc. trying to narrow down the problem. But there surely must be a better way, right?.

So, is there a way to get PHP to produce useful error message like Java does? Can anyone recommend good PHP debugging tips, tools and techniques?

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/

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

    • You can include the following lines in the file you want to debug: 

    error_reporting(E_ALL);
ini_set('display_errors', '1');

    This overrides the default settings in php.ini, which just make PHP report the errors to the log.

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