php - How to print a debug log?

Question

I'd like to debug some PHP code, but I guess printing a log to screen or file is fine for me.

How should I print a log in PHP code?

The usual print/printf seems to go to HTML output not the console.

I have Apache server executing the PHP code.

Answer 1

A lesser known trick is that mod_php maps stderr to the Apache log. And, there is a stream for that, so file_put_contents('php://stderr', print_r($foo, TRUE)) will nicely dump the value of $foo into the Apache error log.