Laravel Eloquent Query Using WHERE with OR AND OR?

How do I say WHERE (a = 1 OR b =1 ) AND (c = 1 OR d = 1)

For more complicated queries am I supposed to use raw SQL?

Make use of Logical Grouping (Laravel 7.x/4.2). For your example, it'd be something like this:

Model::where(function ($query) {
    $query->where('a', '=', 1)
          ->orWhere('b', '=', 1);
})->where(function ($query) {
    $query->where('c', '=', 1)
          ->orWhere('d', '=', 1);
});

If you want to use parameters for a,b,c,d in Laravel 4

Model::where(function ($query) use ($a,$b) {
    $query->where('a', '=', $a)
          ->orWhere('b', '=', $b);
})
->where(function ($query) use ($c,$d) {
    $query->where('c', '=', $c)
          ->orWhere('d', '=', $d);
});

if you want to use parentheses in laravel 4 and don't forget return
In Laravel 4 (at least) you need to use $a, $b in parentheses as in the example

$a = 1;
$b = 1;
$c = 1;
$d = 1;
Model::where(function ($query) use ($a, $b) {
    return $query->where('a', '=', $a)
          ->orWhere('b', '=', $b);
})->where(function ($query) use ($c, $d) {
    return $query->where('c', '=', $c)
          ->orWhere('d', '=', $d);
});

This is my result:

Incase you're looping the OR conditions, you don't need the the second $query->where from the other posts (actually I don't think you need in general, you can just use orWhere in the nested where if easier)

$attributes = ['first'=>'a','second'=>'b'];

$query->where(function ($query) use ($attributes) 
{
    foreach ($attributes as $key=>value)
    {
        //you can use orWhere the first time, doesn't need to be ->where
        $query->orWhere($key,$value);
    }
});