In a custom module, get return of hook for making it available in other hook

Question

I had some similar questions here, but would like ultimately to know best practices and possibilities for this case.

I have my custom module, in which I use two contrib modules hooks. As I understood, hooks are self-invoked (looking from my module point of view), and as soon as I am declaring it, they get executed.

That said, how I can get return of an hook function ?

I am trying to make $foo1 available in other hook and vice versa for $hook2. I would like to avoid oop solutions if possible.

Example:

function mymodule_contribmodulehook1 ($parameter1, $parameter2) {
  //$foo2 here somehow ? 
  $foo1 = 1;
  return $foo1; 
}

function mymodule_contribmodulehook2 ($parameter1, $parameter2) {
  //$foo1 here somehow ?
  $foo2 = 1;
  return $foo2; 
}

Answer 1

This is more like coding problem..

I will create a function that will store the value, the function has two parameters hook name and value. The function will both set and return values based on certain condition. Values will be set corresponding to hook names. While calling the function if we are passing an argument blank then it will return value, if we call the function and pass both arguments then it will set value.

Here's the sample code:

function mymodule_contribmodulehook1 ($parameter1, $parameter2) {
  // $foo2 here somehow ?
  $foo2 = to_and_fro('', 'hook1');
  $foo1=1;
  to_and_fro($foo1, 'hook2'); // Required by hook2.
  return $foo1;
}

function mymodule_contribmodulehook2 ($parameter1, $parameter2) {
  // $foo1 here somehow ?
  $foo1 = to_and_fro('', 'hook2');
  $foo2=1;
  to_and_fro($foo2, 'hook1'); // Required by hook1.
  return $foo2;
}

/**
 * $variable
 * Check whether $variable is present. If present we set the value, otherwise
 * return value.
 *
 * $hook
 * Hook name.
 */
function to_and_fro($variable, $hook) {
  if (!isset($variable)) {
    switch ($hook) {
      case 'hook1':
        return $hook2_var;
      case 'hook2':
        return $hook1_var;
    }
  }
  else {
    switch ($hook) {
      case 'hook1':
        $hook1_var = $variable;
        break;
      case 'hook2':
        $hook2_var = $variable;
        break;
    }
  }
}

Also this will help you if you have more than two hooks, all you need is to increase the number of case and variable inside the custom function.

Hope this helps you!

Answer 2

Yes, if you implement a hook provided by a contrib module, it is invoked by that module function. You can declare those two variables in global scope so that they can be accessible each other in the functions.

<?php
// mymodule.module
global $foo1;
global $foo2;

function mymodule_contribmodulehook1 ($parameter1, $parameter2) {
  global $foo2;
  //$foo2 here 
  $foo1 = 1;
}

function mymodule_contribmodulehook2 ($parameter1, $parameter2) {
  global $foo1;
  //$foo1 here
  $foo2 = 1;
}

If you don't want to use global scope for your variables, you can save and retrieve them alternatively in your Drupal database using variable_set() and variable_get().

function mymodule_contribmodulehook1 ($parameter1, $parameter2) {
  $foo2 = variable_get('foo2');
  $foo1 = 1; 
  variable_set('foo1', $foo1);
}

function mymodule_contribmodulehook2 ($parameter1, $parameter2) {
  $foo1 = variable_get('foo1'); 
  $foo2 = 1;
  variable_set('foo2', $foo2);
}

Note that, for both approaches, you don't need to return each of them as long as you don't have any other purpose.

Answer 3

You can call a hook yourself, so you could write

function mymodule_contribmodulehook1 ($parameter1, $parameter2) {
  $foo2 = mymodule_contribmodulehook2($parameter1, $parameter2);
  $foo1 = 1;
  return $foo1 + $foo2; 
}

function mymodule_contribmodulehook2 ($parameter1, $parameter2) {
  // don't call mymodule_contribmodulehook1 here though, it would result in an infinite loop!
  $foo2 = 1;
  return $foo2; 
}

You might want to refactor the above though:

function mymodule_getFoo1($a, $b) { ... }
function mymodule_getFoo2($a, $b) { ... }

function mymodule_contribmodulehook1 ($parameter1, $parameter2) {
  $foo1 = mymodule_getFoo1($paramater1, $paramater2);
  $foo2 = mymodule_getFoo2($paramater1, $paramater2);
  ...
}

function mymodule_contribmodulehook2 ($parameter1, $parameter2) {
  $foo1 = mymodule_getFoo1($paramater1, $paramater2);
  $foo2 = mymodule_getFoo2($paramater1, $paramater2);
  ...
}