This PHP program demonstrates how to use predefined constants to debug a PHP program.

DebugWithConstants.php

<?php
namespace NTestNamespace;

$fnPrintDiagonostics = function() {
  echo "Directory: ".__DIR__.
    "<br />File: ".__FILE__.
    "<br />Line: ".__LINE__.
    "<br />Namespace: ".__NAMESPACE__.
    "<br />Method: ".__METHOD__.
    "<br />Class: ".__CLASS__.
    "<br />Trait: ".__TRAIT__."<hr />";
};

// Call the anonymous function
echo "<h3>Calling an anonymous function</h3>";
$fnPrintDiagonostics();


function fnTestFunction() {
  echo "Directory: ".__DIR__.
    "<br />File: ".__FILE__.
    "<br />Line: ".__LINE__.
    "<br />Namespace: ".__NAMESPACE__.
    "<br />Method: ".__METHOD__.
    "<br />Class: ".__CLASS__.
    "<br />Trait: ".__TRAIT__."<hr />";
};

// Call a regular function or method
echo "<h3>Calling fnTestFunction()</h3>";
fnTestFunction();


// A very simple trait
trait TTestTrait {
  public function fnTraitFunction() {
    echo "Directory: ".__DIR__.
      "<br />File: ".__FILE__.
      "<br />Line: ".__LINE__.
      "<br />Namespace: ".__NAMESPACE__.
      "<br />Method: ".__METHOD__.
      "<br />Class: ".__CLASS__.
      "<br />Trait: ".__TRAIT__."<hr />";
  }
}

// A simple class
class CTestClass {
  use TTestTrait;
  public function __construct() {
    echo "<h3>Calling fnTestFunction() within the constructor</h3>";
    fnTestFunction();
    echo "<h3>Calling the Constructor</h3>";
    echo "Directory: ".__DIR__.
    "<br />File: ".__FILE__.
    "<br />Line: ".__LINE__.
    "<br />Namespace: ".__NAMESPACE__.
    "<br />Method: ".__METHOD__.
    "<br />Class: ".__CLASS__.
    "<br />Trait: ".__TRAIT__."<hr />";
  }
}

$qObject = new CTestClass();

echo "<h3>Calling fnTraitFunction()</h3>";
$qObject->fnTraitFunction();

?>

Output