I am trying to get list of genes in chromosomal order using file_backend.cgi. I am getting all entries of id with esearch.fcgi which I post all the ids in epost to get WebEnv. Later I use it in file_backend.cgi. I hope to get all gene list but I am limited to 2000 entries. Below is the code:

    set_time_limit( 0 );
    $taxid = '559292';
    $id_list = json_decode(file_get_contents('https://eutils.ncbi.nlm.nih.gov/entrez/eutils/esearch.fcgi?db=gene&term=' . $taxid . '[taxid]&retmode=json'));
    $count = $id_list->esearchresult->count;
    // $count = 1000;
    $id_list = json_decode(file_get_contents('https://eutils.ncbi.nlm.nih.gov/entrez/eutils/esearch.fcgi?db=gene&term=559292[taxid]&retmode=json&retmax=' . $count));
    $cs_id = '';
    foreach ($id_list->esearchresult->idlist as $gene_acc_id) 
    {
        if($cs_id == '') 
        {
            $cs_id = $gene_acc_id;
        }
        else
        {
            $cs_id = $cs_id .',' . $gene_acc_id;
        }
    }
    $env_url = 'https://eutils.ncbi.nlm.nih.gov/entrez/eutils/epost.fcgi';
    $ch = curl_init( $env_url );
    $myvars = 'db=gene&id=' . $cs_id;
    curl_setopt( $ch, CURLOPT_POST, 1);
    curl_setopt( $ch, CURLOPT_POSTFIELDS, $myvars);
    curl_setopt( $ch, CURLOPT_FOLLOWLOCATION, 1);
    curl_setopt( $ch, CURLOPT_HEADER, 0);
    curl_setopt( $ch, CURLOPT_RETURNTRANSFER, 1);
    $response = curl_exec( $ch );
    $xml = simplexml_load_string($response);
    $query_key = $xml->QueryKey;
    $web_env = $xml->WebEnv;
    $download_url = 'https://www.ncbi.nlm.nih.gov/portal/utils/file_backend.cgi?Db=gene&HistoryId=' . $web_env . '&QueryKey=' . $query_key . '&Sort=Chromosome&Filter=all&Mode=file&View=tabular&p$l=Email&BaseUrl=&PortName=live&FileName=&CompleteResultCount=' . $count;
    $tab = file_get_contents($download_url);
    echo $tab;

Any clue how to resolve it?