How to assign a returned Javascript function to a PHP variable and use in an SQL Query?

Question

I use Javascript to get 'member_id' url parameter and need to then assign that value to a PHP variable that I use in an SQL Query. When I simply echo the PHP variable, everything looks good but if I try to include the PHP variable in the SQL query that I submit via POST, I get an error with the SQL Query.

    <script>
var param1var = getQueryVariable("member_id");
function getQueryVariable(variable) {
  var query = window.location.search.substring(1);
  var vars = query.split("&");
  for (var i=0;i<vars.length;i++) {
    var pair = vars[i].split("=");
    if (pair[0] == variable) {
      return pair[1];
    }
  } 
  alert('Query Variable ' + variable + ' not found');
}
</script>

<?php $foo="<script type='text/javascript'>
document.write(getQueryVariable('member_id'));
</script>";
?>

SQL Error: *You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'text/javascript'> document.write(getQueryVariable('member_id')); ')' at line 1*

Marc B · Accepted Answer · 2011-10-27 16:48:40Z

1

PHP executes on the server, Javascript executes on the client. All your php chunklet is doing is outputing a small snippet of Javascript. that javascript is NOT executed on the server. It's sent over to the client and executed in the browser, long after PHP has shut down.

To send data from Javascript back to PHP, you must use an AJAX call, or a normal form submission of some sort.

answered Oct 27, 2011 at 16:48

Marc B

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halfer · Accepted Answer · 2011-10-27 19:16:32Z

0

This is because PHP is run on the server, and your JS executes on the client. Just as an aside, you can do things the other way, so in JS:

<script type="text/javascript">
    var myval = '<?php echo $myphpval ?>';
</script>

This is possible because the PHP executes on the server before the JS executes on the client. If however you want to send a JS value to a PHP script, then you will need to do it after the DOM has loaded, usually via an AJAX call.

edited Oct 27, 2011 at 19:16

answered Oct 27, 2011 at 16:48

halfer

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2 Comments

user1011713 Over a year ago

That's my problem, passing the variable to the sql query so I don't think I could do it backwards.

halfer Over a year ago

Yes, I mentioned that just as an aside. See my last para - or Marc B's post - on what to do instead :)

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