Detect if a method call was from inside the class or outside

caller-history.php

<?php
class Internal {
	public function whosGonnaCall() {		
		$backtrace = debug_backtrace();
		assert(is_array($backtrace));
		assert(is_array($backtrace[1]));
		assert(isset($backtrace[1]['class']));
		
		$callerClass = $backtrace[1]['class'];
		$thisClassName = get_class($this);
		assert($thisClassName == 'Internal');
		
		$callerIsSelf = false;
		if ($thisClassName == $callerClass) {
			$callerIsSelf = true;
		}
		
		$returnString = null;
		if ($callerIsSelf) {
			assert($callerIsSelf == true);
			$returnString = 'Method called by $this';
		} else {
			assert($callerIsSelf == false);
			$returnString = 'Method not called by $this';
		}
		
		return $returnString;
	}
	
	public function callGhostbusters() {
		return $this->whosGonnaCall();
	}
}

class External {
	public function callGhostbusters() {
		$internal = new Internal();
		
		return $internal->whosGonnaCall();
	}
}

$internal = new Internal();
$response = $internal->callGhostbusters();
assert($response == 'Method called by $this');

$external = new External();
$response = $external->callGhostbusters();
assert($response == 'Method not called by $this');
?>