Get code line and file that's executing the current function in PHP?

Question

Imagine I have the following situation:

File1.php

<?php
 include("Function.php");
 log("test");
?>

Function.php

<?php
 function log($msg)
 {
  echo "";
 }
?>

I want to change the log function so that it would produce the following:

test (file: File1.php, line number: 3)

So, any way to get the file name and the line number of the code that executed the current function in PHP?

EDIT for backlog usage comments: When I use backlog in my object oriented way of programming I have the following situation.

Index.php

<?php
 include("Logger.static.php");
 include("TestClass.class.php");
 new TestClass();
?>

TestClass.class.php

<?php
 class TestClass
 {
   function __construct()
   {
     Logger::log("this is a test log message");
   }
 }
?>

Logger.static.php

<?php
 class Logger
 {
   static public function log($msg)
   {
     $bt = debug_backtrace();
     $caller = array_shift($bt);
     echo $caller['file'];
     echo $caller['line'];
   }
 }
?>

This example will return as file "Index.php" and as line number 4, this is where the class is initiated. However, it is supposed to return the file TestClass.class.php and line number 6. Any idea how to fix this?

Answer 1

debug_backtrace() can be used to trace back through the call stack. It can be slow though, so be careful with it if you're doing a lot of logging.

If you're using PHP 5.3, you could take advantage of late static binding and have a base class method of log(), and your child classes could call it but still maintain static references to __FILE__ and __LINE__.

A final option would be just pass __FILE__ and __LINE__ in as parameters when you call your log() function.

Answer 2

You can use debug_backtrace().

http://us3.php.net/manual/en/function.debug-backtrace.php

So, in your log function, you would be able to retrieve the filename and line number from which the log function was called.

I'm using this approach in my logging classes and it has significantly reduced the amount of code required to get meaningful log data. Another benefit would be readability. Magic constants tend to get quite ugly when mixed with strings.

Here's a quick example:

function log($msg)
{
  $bt = debug_backtrace();
  $caller = array_shift($bt);

  // echo $caller['file'];
  // echo $caller['line'];

  // do your logging stuff here.    
}