Executing scripts in order using PHP and MySQL

Question

I have a website that lets user select test scripts from radio buttons, and after submitting the desired test to the remote server, using PHP:

1. It inserts sends a row into MySQL database in the test_activity_log table, with id, username, test name, gateway name, and timestamp.
2. It then sends a ssh2_exec to execute the desired script on the remote gateway

Everything above I already have working, however, in the case when multiple users are executing scripts from the webpage simultaneously, I need to find a way to queue them up in order and execute them one after another. What would be the best way to do this?

Any ideas would be much appreciated.

EDIT:

testexe.php

<?php

...
...    

//while there are still jobs that are not done..
while (1) {
    //wait for 10 seconds and query again...
    sleep(10);
    $statusResult = mysqli_query($dbConnection, $qStatus);
    //if there are undone jobs we pick them and execute them
    if (mysqli_num_rows($statusResult) > 0){
        //query the next undone test case
        $testResult = mysqli_query($dbConnection, $qNextTest);

        //fetch the returned query object and store needed parameters 
        $row = $testResult->fetch_assoc();
        $id = $row['id'];               
        $test_script = $row['test_script']; 
        $gateway = $row['gateway'];         


        if ($connection = @ssh2_connect($gateway, 22)) {
            ssh2_auth_password($connection, $user, $password);

            //execute the test case
            $stream = ssh2_exec($connection, "/my/path/to/script.sh"); 

            //fetch output stream and stderr
            stream_set_blocking($stream, true);
            $stream_out = ssh2_fetch_stream($stream, SSH2_STREAM_STDIO);
            $stream_err = ssh2_fetch_stream($stream, SSH2_STREAM_STDERR);
            while($line = fgets($stream_out)) {flush(); echo '<pre>' . $line . '</pre>';}               
            echo '<pre>' . "------------------------\n" . '</pre>';
            while($line = fgets($stream_err)) {flush(); echo '<pre>' . $line . '</pre>';}
            fclose($stream);    

            //update the table after the above script is done
            $qUpdateStatus = "UPDATE table SET status = 1 WHERE id = $id";
            $updateresult = mysqli_query($dbConnection, $qUpdateStatus);
        }

    }
}

?>