Question

How do I pass a variable to create_function() ?

I have something like this:

function my_hook_function(){
  $var = 10;
  apply_filters('hook', $var);
  return $var;
}


$variable = 5;
$function = create_function('', 'return $variable;');

add_filter('hook', $function); 

echo my_hook_function();

but it doesn’t work 🙁
theoretically the output should be 5

add_filter() is a wordpress function that allows you to change stuff around 🙂

Answer 1

There are two problems here. The first one is that you need to tell php what parameters get passed to the ‘created’ function, or reference them as a global inside of the body. The second is that you are expecting $var to be modified by the created function, but you are not passing it a reference. the created function simply returns the new variable and you do nothing with it.

function my_hook_function(){
  $var = 10;
  $var = apply_filters('hook', $var);
  return $var;
}

/* This will return 5 by dividing the passed value by 2 and returning the result */
$function = create_function('$variable', 'return $variable/2;');    
add_filter('hook', $function);
echo my_hook_function();

/* This will return 5 by referencing the global $variable */
$variable = 5;
$function = create_function('', 'global $variable; return $variable;');
add_filter('hook', $function);
echo my_hook_function();

Note that if you run this code exactly like this that both of the filters will be added to the ‘hook’ hook.