PHP CURL about curl_multi_getcontent overflow

Question

I am use curl connect and use keep alive.When I use curl_multi_getcontent to get data that will display history data in return.

Is it will have problem for example variable overflow? I have searched information that php variable can request size about 2GB. Or any method can solve it? for example disconnect then reconnect to clear curl_multi_getcontent's data?

Because I continue run script now and without any problem. But I don't know script run long away will have problem? below my code

<?php
set_time_limit(0);
$ch = create();
$mh = curl_multi_init();
curl_multi_add_handle($mh, $ch);
$old_data = "";

$data_len = 0;
$running=null;

curl_multi_select($mh);

$active = null;
// execute the handles
do {
    $mrc = curl_multi_exec($mh, $active);
}while ($mrc == CURLM_CALL_MULTI_PERFORM);

while ($active && $mrc == CURLM_OK) {
    if (curl_multi_select($mh) != -1) {
        do {
            $mrc = curl_multi_exec($mh, $active);
            echo str_repeat(" ",1024*5);
            $data = curl_multi_getcontent($ch);
            $pattern = "/--\w*/";
            preg_match_all($pattern, $data, $matches);
            if(sizeof($matches[0]) > 0)
            {
                $split_txt = $matches[0][sizeof($matches)-1];
                $data_list = explode ($split_txt,$data);
                $data_len = count($data_list);
                if($data_len >=2 && $old_data !== $data_list[$data_len-2])
                {
                    $old_data = $data_list[$data_len -2];
                    $time_pattern = "/-\d{19}/";
                    preg_match($time_pattern, $old_data, $time_matches);
                    $time = $time_matches[0];
                    echo($old_data."<br>");
                    $write_txt = time_covert($time).":  ".$old_data;
                    $file = fopen("output.txt","a");
                    fwrite($file,$write_txt);
                    fclose($file);
                }
            }
        } while ($mrc == CURLM_CALL_MULTI_PERFORM);
    }
}