PHP Warning demolishes JSON response

Question

I'm implementing an ajax fileupload for my php application (using CodeIgniter).

I detect if the uploaded POST data is to large (>post_max_size) according to http://andrewcurioso.com/2010/06/detecting-file-size-overflow-in-php/ and try to send an appropriate JSON-encoded error response.

But the corresponding php warning included in the output completely destroys my JSON response !

<br />
<b>Warning</b>:  POST Content-Length of 105906405 bytes exceeds the limit of 8388608 bytes in <b>Unknown</b> on line <b>0</b><br />
[{"error":"Posted data is too large. 105906405 bytes exceeds the maximum size of 8388608 bytes."}]

I don't want to parse and filter the warning out on client side, that seems ugly. And disabling all php warnings globally seems inappropriate.

Can I disable specific PHP warnings in the context of a php function? Or wrap it inside of a valid json response?

Answer 1

On production server: Always disable php warnings.

On development machine: Disable all warnings for that page for the purpose of testing and re-enable after testing is complete and functionality confirmed as working.

Hint: I prefer to have a variable globally set and depending on that enable or disable all php and database warning notifications. You could set that in .htaccess for example if you use apache. I have this in .htaccess:

• production: SetEnv DEVELOPMENT Off
• development: SetEnv DEVELOPMENT On

And in the php code:

if( strtolower(getenv('DEVELOPMENT')) == "on" ) {
        ini_set("display_errors",2);
        ini_set('error_reporting', E_ALL | E_STRICT);
}

To disable all errors from .htaccess use

php_flag display_startup_errors off
php_flag display_errors off
php_flag html_errors off
php_value docref_root 0
php_value docref_ext 0

If you want to get really tricky you could add a check like:

if(error_get_last() !== null)

and set a http header and check that from javascript both for json output and when loading your page and take a look at the error log or display the error on screen if you prefer that, still I strongly recommend that you disable the error showing code in the production environment.

For more in-depth talk about this take a look at this article.