<?php
spl_autoload_register(function ($name) {
    echo "Want to load $name.\n";
   
});

spl_autoload_register(function($className) {
    var_dump($className);
});

function unregister($className) {
    var_dump($className.' i will be the first');
}

spl_autoload_register('unregister');

var_dump(spl_autoload_functions());

===================

array(3) {
  [0]=>
  object(Closure)#1 (1) {
    ["parameter"]=>
    array(1) {
      ["$name"]=>
      string(10) "<required>"
    }
  }
  [1]=>
  object(Closure)#2 (1) {
    ["parameter"]=>
    array(1) {
      ["$className"]=>
      string(10) "<required>"
    }
  }
  [2]=>
  string(10) "unregister"
}