Questions about concurrent curl

I use curl_multi_init and a series of related methods to implement concurrent stress testing of the interface. The curl code is placed on the a server and the tested interface is placed on the b server. The two servers are intranets.
my test code is roughly as follows

$chlist = [];
    foreach($requestList as $k=>$v){// 500
        $chlist[$k]=curl_init();
        curl_setopt($chlist[$k], CURLOPT_URL, $sysConfig["apiUrl"]);// 
        curl_setopt($chlist[$k], CURLOPT_RETURNTRANSFER, 1);
        curl_setopt($chlist[$k], CURLOPT_CUSTOMREQUEST, "POST");
        curl_setopt($chlist[$k], CURLOPT_HTTPHEADER, array("Accept-Encoding:gzip"));
        curl_setopt($chlist[$k], CURLOPT_ENCODING, "gzip");
        curl_setopt($chlist[$k], CURLOPT_HTTPHEADER, array (
            "Content-Type: application/x-www-form-urlencoded; charset=gbk", 
        ));
        // 
        $reqXml = "<Req funcid="9999"><![CDATA[".parameHandle($v["params"],$apilist[$v["api"]]["paramsType"])."]]></Req>";
        $seKey = getRndString();
        $dateKey = getDateString();
        $strPost = encode($reqXml, $sysConfig["key"], $sysConfig["version"], $sysConfig["chan_code"], $seKey, $dateKey);// 
        curl_setopt ( $chlist[$k], CURLOPT_POSTFIELDS, $strPost );
        curl_setopt($chlist[$k], CURLOPT_TIMEOUT,120);   
    }

    $mh = curl_multi_init();

    foreach($chlist as $k=>$v) {
        curl_multi_add_handle($mh,$v);
    }
    $active = null;
    $start=time();
    var_dump($start);// 
    // 
    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, $active);
            } while ($mrc == CURLM_CALL_MULTI_PERFORM);
        }
    }
    $end = time();
    var_dump($end);// 
    var_dump($end - $start);// 

    //4.curl
    foreach($chlist as $val){
        curl_multi_remove_handle($mh, $val);
        $response[] = curl_multi_getcontent($val);
    }
    //5.curl
    curl_multi_close($mh);
    //var_dump($response);
    return $response;

but I doubt whether such a test is accurate. I have seen that when the test program is running, the top, usage of a server is not full, but the result of my test takes at least ten seconds, while the developer of the interface uses apache jmeter to test 500concurrency, only 5 seconds. What is the reason for this?

I tried again. Before I opened the test code, I used the browser to access the code address, but now it is executed on the command line, and the speed is obviously shorter, almost or even a little faster than apache jmeter, so it is the reason why the browser remote access takes up the network speed?

Php

Mar.25,2021