CHAPTER 8 How to Fix The Web: Obscure Back-End Techniques and Terminal Secrets
above has worked, then give it some consideration. Deep within your code,
you may have a function which calls some other function, which calls the
original function in an infinite recursion.DebuggeRS
If you’ve gotten this far, and your page is still not showing up, then you’re
entering more difficult territory. Your PHP may be executing validly
and doing everything it should, but there’s some logical error in your
programming. For quick debugging you can var_dump variables to the
browser, perhaps wrapping them in an if statement so that only your IP
address sees them:<? if ($_SERVER['REMOTE_ADDR'] == '85.106.118.199') var_dump ($product); ?>This method will narrow down an error but it is ungraceful and error-
prone, so you might consider a debugging tool such as Xdebug or FirePHP.
They can provide masses of information, and can also run invisibly to the
user, saving their output to a log file. Xdebug can be used like this:<?
ini_set ('xdebug.collect_params', 1);
xdebug_start_trace ('/tmp/xdebugtrace');
echo "This will get traced.";
xdebug_stop_trace();
?>This bit of code logs all function calls and arguments to the file /
tmp/xdebugtrace.txt. It displays even more information when there is a
PHP notice or error. However, the overhead may not be suitable for a live
environment, and it needs to be installed on the server, so it’s probably not
available in most hosting environments.
FirePHP, on the other hand, is a PHP library that interacts with an add-
on to Firebug, a plugin for Firefox. You can output debugging information
and stack traces from PHP to the Firebug console.