Serve multiple pages from 1 PHP file?

Question

So basically i am struggling with the need of optimizing my code for some project of mine. Currently i have pages like add_company.php, view_company.php

Answer 1

This is pretty simple stuff. It should look something like this:

//index.php
if (!isset($_GET['page']))
    {
    require('index_contents.php');
    }
else if ($_GET['page'] == 'company')
    {
    if (!isset($_GET['action']))
        {
        require('company_contents.php');
        }
    else if ($_GET['action'] == 'edit')
        {
        require('edit_company.php');
        }
    else if ($_GET['action'] == 'add')
        {
        require('add_company.php');
        }
    else
        {
        require('company_contents.php');
        }
    }
else
    {
    require('index_contents.php');
    }