多个链接，多个GET []

I Am currently writing My first big project.

I have a navbar with many links that now are linking to "index.PHP?a=value&b=value"

On My index page i have the following:

if((($_GET['a']) == "value") && (($_GET['b']) == "value")) {
     *** soms code ***
}
if((($_GET['a']) == "value") && (($_GET['b']) == "value2")) {
     *** soms code ***
}

Etc...

But with 50 are more links My index.PHP file Will get a Little bit clutterd.

I have thinking of changing the code to:

if((($_GET['a']) == "value") && (($_GET['b']) == "value")) {
     include("somefile.php");
}

Wat is the best way to go around this ? Maybe the onclick=.. ?

Please your thoughts on this

you can simplify like that

if ($_GET['a'] == "value") {

    if ($_GET['b'] == "value") {
         *** soms code ***
    } elseif ($_GET['b'] == "value2") {
         *** soms code ***
    } elseif ($_GET['b'] == "value3") {
         *** soms code ***
    }

    // ...

}

or if you want to have your code in more files, try this :

if (    isset($_GET["a"])
    &&  isset($_GET["b"])
) {
    // security : cut all but a-z
    $a = preg_replace("![^a-z]!", "", $_GET["a"]);
    $b = preg_replace("![^a-z]!", "", $_GET["b"]);

    // include the file
    include "files/part1-$a-part2-$b.php";
}

You write a big project. Why don't you use a serious framework as Laravel, etc? That make it less complex for you to make a scalable and maintainable application.

Separate routing from your index. Separate responsibilities (presentation, business logic, etc.)

Read more about effective routing in Laravel: http://laravel.com/docs/master/routing#basic-routing

This is a problem solved long ago. In modern frameworks it is called routing, you can look it up.

A simplified example would be to have an array mapping values to files on the system, and then call a function to include the appropriate file.

$routes = [
    'value1' => ['value1' => 'file1.php'],
    'value2' => ['value2' => 'file2.php']
]

function route($value1, $value2) {
    global $routes;
    require($routes[$value1][$value2];
}

Then in index.php you just call

route($_GET['a'], $_GET['b']);

This example is not to be taken literally, it is just an illustration

As suggested in another answer, it is probably a good idea to consider using a framework. They exist for a reason.