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*

Answer 1

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.