ReflectionClass::getMethods() sorts the methods by class (lowest in the inheritance tree first) then by the order they are defined in the class definition:
<?php
class A {
 public function method1() {
 
 }
 
 public function method2() {
 
 }
}
class B extends A {
 public function method3() {
 }
 public function method4() {
 }
}
$class = new ReflectionClass('B');
print_r($class->getMethods());
?>

This will output:
Array
(
 [0] => ReflectionMethod Object
 (
 [name] => method3
 [class] => B
 )
 [1] => ReflectionMethod Object
 (
 [name] => method4
 [class] => B
 )
 [2] => ReflectionMethod Object
 (
 [name] => method1
 [class] => A
 )
 [3] => ReflectionMethod Object
 (
 [name] => method2
 [class] => A
 )
)