Bugfix

[ianitsky]

ContextErrorException: Notice: Undefined index: CURLOPT_HTTPHEADER

Fixes #45

[TobiasHauck]

First of all: Thank you for contributing! And sorry for being that late.

In general your bugfix is a good one. But we just need to clean up the code a bit. If you had a look at the rest of the code we tried...
... not to mutate existing variables and
... not to create/mutate variables in a branch

Example:

    if($x) {
        $var = 'value';
    } else {
        $var = 'anotherValue';
    }

turns to

$var = $x ? 'value' : 'anotherValue';

The idea is to use conditions as statements instead of expressions to ensure we don't generate side effects.

So what we need here is something like:

    if(!empty($idColumns)) return end($idColumns);

    $reservedTokens = array_filter($tokens['SELECT'], function($token) {
        return $token['expr'] === 'reserved';
    });

    $finalTokens = count($reservedTokens) > 0 ? $reservedTokens : $tokens;

    return end($finalTokens[0]['no_quotes']['parts']);

Maybe I missed a detail, but I hope it helps you to understand what I want to change here.
May you be so kind and change these few lines so I can merge the PR?