<?php
 
class firstClass {
 
    public function firstMethod() {}
    private function secondMethod() {}
 
}
 
class secondClass extends firstClass {
 
    public function thirdMethod() {}
    private function fourthMethod() {}
 
}
 
function check_method($obj, $methodName)
{
    $class = new ReflectionClass($obj);
	$methods = $class->getMethods();
	return [] != array_filter($methods, function($v) use ($methodName, &$obj) {
    	return $v->name === $methodName && $v->class === get_class($obj);
	});
}
 
$obj = new secondClass;
$methodName = 'firstMethod';
var_dump(check_method($obj, $methodName));

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