Setting "--keepalive-time" for curl in php

Question

Some backstory here: https://serverfault.com/questions/714273/curl-returning-error-52-or-56-with-rest-api-call-spanning-more-than-5-minutes

So, I have this REST API call that I need to make via PHP and the only way I can get it to work via the CLI is setting the --keepalive-time for CURL. So how do I do that in PHP? Here is the (censored for creds) working API call via CURL directly:

curl --max-time 600 -k -o dump.txt --connect-timeout 0 --keepalive-time 30 --trace-ascii trace.txt --trace-time -X GET -H "tenant-code: 1cmPx7tqVDVTdN1GSelwycFUmICmASnLCmNQsV72" -H "Authorization: Basic JxHAsXeUiHMRkS8Msiu6pWb3PvY20p6am3QvXCY3knXTAntlxTBS3EyEDgly" -H "Content-Type: application/json" -H "Cache-Control: no-cache" 'https://api.endpoint.com/API/v1/system/users/search?groupid=555'

The --max-time and --connect-timeout values don't seem to matter as much (as long as they are within bounds of what I need) but the --keepalive-time seems to be required to get the data back from the call. Here is some test code I am using:

<?php
$url = "https://api.endpoint.com/API/v1/system/users/search?groupid=555";
$session = curl_init($url);
curl_setopt($session,CURLOPT_RETURNTRANSFER, true);
curl_setopt($session,CURLOPT_TIMEOUT, 600);
curl_setopt($session, CURLOPT_RETURNTRANSFER, true);
curl_setopt($session, CURLOPT_AUTOREFERER, true);
curl_setopt($session, CURLOPT_FOLLOWLOCATION, true);
curl_setopt($session, CURLOPT_VERBOSE, true);
curl_setopt($session, CURLOPT_CONNECTTIMEOUT, 0);
curl_setopt($session, CURLOPT_NOPROGRESS, false); 
curl_setopt($session, CURLOPT_FORBID_REUSE, true);
curl_setopt($session, CURLOPT_FRESH_CONNECT, true);
$headers = array(
        'tenant-code: 1cmPx7tqVDVTdN1GSelwycFUmICmASnLCmNQsV72',
        'Authorization: Basic JxHAsXeUiHMRkS8Msiu6pWb3PvY20p6am3QvXCY3knXTAntlxTBS3EyEDgly',
        'Cache-Control: no-cache',
        'Accept: application/json');
        curl_setopt($session, CURLOPT_HTTPHEADER, $headers);
$output = curl_exec($session);
$httpcode = curl_getinfo($session, CURLINFO_HTTP_CODE);
curl_close($session);
var_dump($httpcode, $output, $session, $headers, $url);
?>

I added curl_setopt($session, CURLOPT_FORBID_REUSE, true); and curl_setopt($session, CURLOPT_FRESH_CONNECT, true); for testing but they don't seem to have any effect on my issue. So what is needed to get this handled by CURL in PHP?

Answer 1

If you are using PHP 5.5 or greater (currently 5.5, 5.6, & 7) built with cURL 7.25.0 or greater, you can set these cURL options in PHP to match the --keepalive-time parameter (PHP <= 5.4 did not have these cURL options available):

curl_setopt($session, CURLOPT_TCP_KEEPALIVE, 1);
curl_setopt($session, CURLOPT_TCP_KEEPIDLE, 30);
curl_setopt($session, CURLOPT_TCP_KEEPINTVL, 15);

The CURLOPT_TCP_KEEPIDLE constant in libcurl corresponds to the --keepalive-time command line option for curl.

See the cURL docs regarding CURLOPT_TCP_KEEPALIVE, CURLOPT_TCP_KEEPIDLE, and CURLOPT_TCP_KEEPINTVL for more info.

Note: These options are not available and can't be used if you have PHP 5.4 or lower.