PHP语句被忽略？

Question

    echo 'position: '.$position.'<br/>district: '.$district;
    if($position == 0 && $district == 0){
        $results = DB::table('salaries')
            ->join('districts', 'salary_district', '=', 'district_id')
            ->join('companies', 'salary_company', '=', 'company_id')
            ->join('positions', 'salary_position', '=', 'position_id')
            ->paginate($pages);
       echo '<br/>first';
    } elseif($district == 0 && $position != 0){
        $results = DB::table('salaries')
            ->join('districts', 'salary_district', '=', 'district_id')
            ->join('companies', 'salary_company', '=', 'company_id')
            ->join('positions', 'salary_position', '=', 'position_id')
            ->where('position_name', '=', $position)
            ->paginate($pages);
        echo '<br/>second';
    } else {
        $results = DB::table('salaries')
            ->join('districts', 'salary_district', '=', 'district_id')
            ->join('companies', 'salary_company', '=', 'company_id')
            ->join('positions', 'salary_position', '=', 'position_id')
            ->where('position_name', '=', $position)
            ->where('district_id', '=', $district)
            ->paginate($pages);
        echo '<br/>third';
    }

输出：

position: Contabilista
district: 0
first

$position contabilista与true进行比较时，0给我{{1}}的情况如何？我错过了什么？