PHP Magic Constants

<?php
 
 class Foo {
   // Use the __CLASS__ constant to log the class
   public $message = '';
 
   function bar_one() {
    	// Use the __CLASS__ and __FUNCTION__ constants to	    	
    	// log the class name and the specific function the
    	// constant is found in.
    	$this->message .= 'Class:  ' . __CLASS__;
    	$this->message .= ', Function: ' . __FUNCTION__;
   }
 
   function bar_two() {
    	// User the __METHOD__ constant to log the class's method
    	$this->message .= ', Method: ' . __METHOD__;
   }
 
   function log_message() {
    	// Name the error log file
    	$error_log = 'error_log_' . date('D_M_j_G_i_s');
 
    	// Use the __LINE__ constant to provide a line number
    	$this->message .= ', Line: ' . __LINE__;
    	// Write the log file
    	file_put_contents($error_log, $this->message, FILE_APPEND);
   }
 }
 
 $object = new Foo();
 $object->bar_one();
 $object->bar_two();
 $object->log_message();
 
 // Outputs
 // Class:  Foo, Function: bar_one, Method: Foo::bar_two, Line: 25
?>