Run External PHP File From Joomla Article

Question

I have a PHP file that will echo results in the end of the file. I want to fire some Javascript from an onclick event that will call this PHP file and print the results on screen. My Javascript looks like this, but I get a 500 error, and am not sure why.

What is incorrect in my syntax? Or what is the proper way to do this in Joomla 3.5?

<form id="HomePage" method="post">
<div style="padding-top: 10px;"><input type="submit" value="Submit" id="ajaxButton" /></div>
<div style="padding-top: 10px;">&nbsp;</div>
</div>
<script type="text/javascript">
(function() {
  var httpRequest;
  document.getElementById("ajaxButton").onclick = function() { makeRequest('Test.php'); };

  function makeRequest(url) {
    httpRequest = new XMLHttpRequest();

    if (!httpRequest) {
      alert('Giving up :( Cannot create an XMLHTTP instance');
      return false;
    }
    httpRequest.onreadystatechange = alertContents;
    httpRequest.open('GET', url);
    httpRequest.send();
  }

  function alertContents() {
    if (httpRequest.readyState === XMLHttpRequest.DONE) {
      if (httpRequest.status === 200) {
        alert(httpRequest.responseText);
      } else {
        alert('There was a problem with the request.');
      }
    }
  }
})();
</script>
</form>

EDIT
This is the contents of my Test.php. Does this look incorrect? If I add this directly to an article, it returns the result that I want, but for some reason I can't get the syntax correct for calling it from a separate article.

<?php
    $option = array(); 

    $option['driver']   = 'mssql';
    $option['host']     = 'host';
    $option['user']     = 'user';       
    $option['password'] = 'password';   
    $option['database'] = 'database';     
    $option['prefix']   = '';            

    $db = JDatabase::getInstance( $option );
    $result = $db->getQuery(true);
    $result->select($db->quoteName(array('trackandfieldresults')));
    $result->from($db->quoteName('[TrackData]')); 
    $db->setQuery($result); 
    $row = $db->loadRowList();
    echo $row['0']
?>

EDIT
Updated PHP File

<?php

$serverName = "ServerName"; 
$uid = "sqlusername";   
$pwd = "sqlpassword";  
$databaseName = "DBName"; 

$connectionInfo = array( "UID"=>$uid,                            
                         "PWD"=>$pwd,                            
                         "Database"=>$databaseName); 

$conn = sqlsrv_connect( $serverName, $connectionInfo);

if( $conn ) {
     echo "Connection established.<br />";
}else{
     echo "Connection could not be established.<br />";
     die( print_r( sqlsrv_errors(), true));
}
?>

Answer 1

1. I just pasted your code into an article on the home page of a joomla 3.6 site and put a Test.php at the root of the too and it worked fine. To my mind if you are doing exactly that then there is a problem with your php file cause in this request Joomla is not really involved (Note for 500 errors the first thing I would look at would be the file's permissions).

2. This approach is fine if your the only dev on the site and your php doesn't interact with Joomla at all. Joomla provides a simple way to make ajax requests with modules using the com_ajax interface: doc is here. This would be neater, more portable, less prone to accidental breakage, and give you access to the Joomla application - on the other hand, the Joomla app has to load fully so you'll lose some microseconds.