Get PHP child Class file paths from inherited parent class methods

child-filepath.md

Get PHP child Class file paths from inherited parent class methods

While refactoring some code into a reusable PHP Class I hit a brief roadblock where some code expected the __FILE__ magic constant file path. Since that value always refers to the specific file it's called from, it won't work from a separate Class file because the referenced path would be the parent instead of the child.

The full filepath of a child Class can be inferred from an inherited parent Class method by combining get_class($this) or get_called_class() with the ReflectionClass::getFileName method like this:

// ParentClass.php
class ParentClass
{
    public function __construct()
    {
      $childRef = new \ReflectionClass(get_class($this));
        echo __FILE__;
        echo "\n";
        echo $childRef->getFileName();
    }
}

// ChildClass.php
class ChildClass extends ParentClass
{
}

// index.php
require 'ParentClass.php';
require 'ChildClass.php';

new ChildClass();

Output:

/var/www/html/ParentClass.php
/var/www/html/ChildClass.php

For some reason, this was difficult to search for, but eventually I found this ancient Stack Overflow answer which got me most of the way there.