Why are route parameters misaligned when using dynamic domain placeholders in Laravel?

When you use a dynamic domain (with a placeholder like {domains_eu}) in a route group, Laravel “inserts” that matched value as the first route parameter. This means that even if your route only defines {param} after the URL path, your controller will actually receive two parameters. There are two ways to fix this:

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1. Update Your Controller Signature

Update the method that handles the route so that it accepts the extra (domain) parameter. For example, change:

PHPCopied
// Before – expecting just one parameter:
public function somePage($param)
{
    // ...
}

to

PHPCopied
// After – account for the injected domain parameter:
public function somePage($domains_eu, $param)
{
    // You can ignore $domains_eu if not needed
}

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2. Remove the Dynamic Domain Parameter

If you don’t need the domain value in your controller and want to avoid the extra parameter, then do not use a dynamic group domain. Instead, set up your routes without a placeholder in the domain. For example:

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Route::pattern('domains_eu', '(domaina\.eu|domainb\.eu|domainc\.eu)');
Route::group(['domain' => 'domaina.eu'], function () {
    Route::get('/somepage/{param}', 'HomeController@somePage');
});

However, note that this forces a static domain for the group. If you need the group to handle multiple domains, then the first approach is the correct one.

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Conclusion

The solution is to recognize that by using a dynamic domain placeholder (like {domains_eu}), Laravel automatically adds it as a route parameter. Therefore, the controller method must accept it as its first parameter (whether or not you use it), or else the parameters will “shift” and lead to errors.