Drupal 8 : How to write custom php functions and call the function from a custom page?

Question

I am new to Drupal web development. I have already used Wordpress platform by building a custom plugin to write custom php functions, and calling the function from a custom page was easy.

example:

<?php
function givenumber(){
  return 50;
}
?>;

Which I call by using:

<?php  echo givenumber(); ?>

How can I achieve similar with Drupal 8?
Do I need to create a custom module for writing the custom php functions?
How do I call a function from a custom page?

Please help.

baikho baikho · Accepted Answer · 2020-04-09T12:52:15

The best way to do this in Drupal 8 is to create a service in a custom module yes.

Create a module with the following structure:

your_custom_module/
├── your_custom_module.info.yml
├── your_custom_module.services.yml
└── src/
    └── YourCustomService.php

Your your_custom_module.services.yml file:

services:
  your.custom.service:
    class: Drupal\your_custom_module\YourCustomService

Your Service class:

<?php

namespace Drupal\your_custom_module;

class YourCustomService {

  public function giveNumber() {
    return 1234;
  }

}

Enable the module and you can now call this service:

\Drupal::service('your.custom.service')->giveNumber();

See more details in Structure of a service file

Drupal 8 : How to write custom php functions and call the function from a custom page?

2 Answers