Jackson Bates

Unhelpful Laravel Bug | Undefined offset: 0

Some time wasted on a silly mistake today.

I received Undefined offset: 0 as an error response from my Laravel API. The API call and routes / controllers were identical to other attempts at something similar in other parts of the same codebase.

Numerous Stack Overflow responses explain that this happens when a database record that does not exist is referenced. However, this was a simple GET request that was failing at even returning a simple string with no attempt at reading from the database, so those responses felt irrelevant.

What was happening? #

The cause of the problem in the end was sloppy API route naming and attempting to (unwittingly) access database records that didn't exist.

Here's an example of the routes:

Route::prefix('resources')->group(function () {
    Route::get('{resource}', 'ResourceController@show');
    Route::get('our-resources', 'ResourceController@showCompanyResources');
    Route::post('response', 'ResourceController@submit');
});

GETs to /api/resources/:resource_id worked fine.

POSTs to /api/resources/response also worked fine.

But GET to /api/resources/our-resources triggered the error.

Now that I type it out, the reason is pretty obvious. GET /api/resources/our-resources is interpreted as a call to /api/resources/:resource_id where the id is our-resources. So the @show method on the controller was intercepting the request, and not finding the correct resource (as it didn't exist in the database).

The routes are tested in the order they are listed, so /api/resources/our-resources is never reached.

Fix #

One quick fix is to change the order of the routes like this:

Route::prefix('resources')->group(function () {
    Route::get('our-resources', 'ResourceController@showCompanyResources');
    Route::get('{resource}', 'ResourceController@show');
    Route::post('response', 'ResourceController@submit');
});

Alternatively, you can use more precise name-spacing for your routes to avoid these clashes.