Debugging Can Be Difficult
Debugging a PHP script can be a difficult task, especially when code is located over many files. Trying to debug a complicated CMS like Drupal, where function calls are not always explicit and may be implemented as hooks, can be an outright nightmare.
Magic Constants
Luckily, PHP has a few not so well known magic constants that can greatly aid developers. I think the most useful of all is the __FUNCTION__ constant. This function will return the name of the function that it is called in. To use effectively add either of the following two statements to the first line of each function in the file(s) of code you are executing:
echo('Current Function: ' . __FUNCTION__); error_log('Current Function: ' . __FUNCTION__);
After you execute your script or page, you will get a chronologically ordered function by function run-down of what has been executed. Note that you must choose either echo or error_log ouput, where appropriate. Echo will output directly to the screen, but may not work as expected in some circumstances where your output is buffered, or echo’s happen amid hidden page elements. The most reliable way is to use error_log() to output to your server’s PHP error log. Unfortunately, this log may not be viewable in some hosted site situations where you have limited access to PHP’s configuration.
Other magic constants are also available for debugging object oriented PHP code including __CLASS__ and __METHOD__. The constant __FUNCTION__ will return the same method information when a function is inside of a class, so you can just use __FUNCTION__ instead of __METHOD__.
The last two magic constants are __FILE__ and __LINE__ which do pretty much exactly what you think they would do. For more information on PHP’s magic constants, check out this PHP manual page.
You are saying “The constant __FUNCTION__ will return the same method information when a function is inside of a class, so you can just use __FUNCTION__ instead of __METHOD__.”
It’s not true. Let’s say you have class like this:
class MyClass
{
function myFunc()
{
throw new Exception(__FUNCTION__);
}
function myMeth()
{
throw new Exception(__METHOD__);
}
}
The result you will get by calling MyClass->myFunc will be “myFunc” whereas the result from myMeth will be “MyClass::myMeth”.