Why I'm getting 'Non-static method should not be called statically' when invoking a method in a Eloquent model?

You defined your method as non-static and you are trying to invoke it as static. That said...

1.if you want to invoke a static method, you should use the :: and define your method as static.

// Defining a static method in a Foo class.
public static function getAll() { /* code */ }

// Invoking that static method
Foo::getAll();

2.otherwise, if you want to invoke an instance method you should instance your class, use ->.

// Defining a non-static method in a Foo class.
public function getAll() { /* code */ }

// Invoking that non-static method.
$foo = new Foo();
$foo->getAll();

Note: In Laravel, almost all Eloquent methods return an instance of your model, allowing you to chain methods as shown below:

$foos = Foo::all()->take(10)->get();

In that code we are statically calling the all method via Facade. After that, all other methods are being called as instance methods.

Why not try adding Scope? Scope is a very good feature of Eloquent.

class User extends Eloquent {

    public function scopePopular($query)
    {
        return $query->where('votes', '>', 100);
    }

    public function scopeWomen($query)
    {
        return $query->whereGender('W');
    }

}

$users = User::popular()->women()->orderBy('created_at')->get();

Eloquent #scopes in Laravel Docs

TL;DR. You can get around this by expressing your queries as MyModel::query()->find(10); instead of MyModel::find(10);.

To the best of my knowledge, starting PhpStorm 2017.2 code inspection fails for methods such as MyModel::where(), MyModel::find(), etc (check this thread). This could get quite annoying, when you try let's say to use PhpStorm's Git integration before committing your code, PhpStorm won't stop complaining about these static method call warnings.

One elegant way (IMOO) to get around this is to explicitly call ::query() wherever it makes sense to. This will let you benefit from a free auto-completion and a nice query formatting.

Examples

Snippet where inspection complains about static method calls

$myModel = MyModel::find(10); // static call complaint

// another poorly formatted query with code inspection complaints
$myFilteredModels = MyModel::where('is_beautiful', true)
    ->where('is_not_smart', false)
    ->get();

Well formatted code with no complaints

$myModel = MyModel::query()->find(10);

// a nicely formatted query with no complaints
$myFilteredModels = MyModel::query()
    ->where('is_beautiful', true)
    ->where('is_not_smart', false)
    ->get();