Set_error_handler function in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the set_error_handler function in PHP?

The set_error_handler function lets you define a custom function to handle errors instead of PHP's default error handler. This helps you control how errors are processed and displayed.

beginner

How do you define a custom error handler function for set_error_handler?

You create a function that accepts parameters like error level, error message, file, and line number. Then you pass its name to set_error_handler to use it for handling errors.

intermediate

What parameters does the custom error handler function receive?

It receives these parameters:

• $errno: The error level
• $errstr: The error message
• $errfile: The file where the error occurred
• $errline: The line number of the error
• $errcontext (deprecated as of PHP 7.2.0): An array of variables in scope

intermediate

What happens if the custom error handler returns false?

If the custom error handler returns false, PHP will execute the default error handler as well. Returning true or nothing prevents the default handler from running.

advanced

Can set_error_handler handle fatal errors like E_ERROR?

No, set_error_handler cannot handle fatal errors like E_ERROR or parse errors. It only handles non-fatal errors like warnings and notices. For fatal errors, you can use register_shutdown_function with error_get_last().

What does set_error_handler do in PHP?

A Logs errors to a file automatically

B Sets a custom function to handle errors

C Stops all errors from occurring

D Fixes syntax errors in code

set_error_handler lets you specify your own function to manage errors instead of PHP's default way.

Which parameter is NOT passed to a custom error handler function?

A $errtrace (stack trace)

B $errstr (error message)

C $errcontext (variables in scope)

D $errno (error level)

The $errtrace parameter is not passed to the error handler. Stack traces are not given automatically.

What happens if your custom error handler returns false?

A PHP runs the default error handler too

B PHP logs the error silently

C PHP stops the script immediately

D PHP ignores the error

Returning false tells PHP to also run its default error handler.

Can set_error_handler catch fatal errors like E_ERROR?

A Yes, always

B Only if error_reporting is set to E_ALL

C No, it cannot

D Only in PHP 8+

Fatal errors are not handled by set_error_handler. Use shutdown functions instead.

Which function can you use to restore the previous error handler?

A remove_error_handler()

B reset_error_handler()

C clear_error_handler()

D restore_error_handler()

restore_error_handler() resets the error handler to what it was before.

Explain how to create and use a custom error handler with set_error_handler in PHP.

Think about the function signature and how PHP calls it on errors.

What types of errors can set_error_handler handle and which ones it cannot?

Consider the difference between recoverable and fatal errors.