Description:
------------
If a SoapClient object is constructed without specifying the 'keep_alive' option to false, the socket never appears to be closed if it falls out of scope

The provided script should be able to reproduce this, you can check the open sockets by running the script like: "php /path/to/script.php &" and using the resulting PID on "lsof -a -p {pid}"

You should slowly see a list of TCP connections slowly build up over time similar to this:

php     4396 vagrant    3u  IPv4  53416      0t0     TCP homestead:57814->ec2-52-7-155-169.compute-1.amazonaws.com:https (ESTABLISHED)
php     4396 vagrant    4u  IPv4  53447      0t0     TCP homestead:57816->ec2-52-7-155-169.compute-1.amazonaws.com:https (ESTABLISHED)
php     4396 vagrant    5u  IPv4  54451      0t0     TCP homestead:57818->ec2-52-7-155-169.compute-1.amazonaws.com:https (ESTABLISHED)

If instead you were to add ['keep_alive' => false] as the options parameter on the SoapClient you'll see that the TCP connections don't appear to build up.

While I do understand the purpose of Keep Alive to keep a single connection open, I would assume this is still a bug as the SoapClient has gone out of scope and new SoapClient objects don't appear to reuse the existing connection and simply ignore it creating a new one.

Test script:
---------------
<?php

function call(int $number) {
    $client = new SoapClient('https://www.dataaccess.com/webservicesserver/NumberConversion.wso?WSDL');
    $response = $client->NumberToWords(['ubiNum' => $number]);
    return $response->NumberToWordsResult;
}

$numbers = array_fill(0, 10000, 1);

foreach ($numbers as $number) {
    call($number);
}

Expected result:
----------------
The socket to be closed when the SoapClient object falls out of scope or destructs

Actual result:
--------------
The socket stays open and contributes to the open file limit / file descriptor limit