wp: hooks simple implementation

simple-hooks.php

<?php

$actions = array();

function add_action($hook, $function) {
  global $actions;

  if (! isset($actions[$hook]))
    $actions[$hook] = array();

  $actions[$hook][] = $function;
}

function do_action($hook) {
  global $actions;

  if (! isset($actions[$hook])) return;

  foreach ($actions[$hook] as $function)
    call_user_func($function);
}

add_action('my_hook_1', function() {
  echo 'hello from my_hook_1', PHP_EOL;
});
add_action('my_hook_2', function() {
  echo 'Hello from my_hook_2!', PHP_EOL;
});

do_action('my_hook_1');
do_action('my_hook_2');