Using PHP value in javascript - working in alert() but not getelementbyid

Question

i am using this:

$newPostID_fromCookie = $_COOKIE['scrollToBottom']+5000;
echo "
  <script>
  window.onload = function () {
    //document.getElementById('$newPostID_fromCookie').scrollIntoView();
    alert('$newPostID_fromCookie');
  }
  </script>
";

This correctly shows the value from the cookie in the alert, but i am getting 'is null' error when trying to use the value in the getElementById.

How can i use the value in this?

Does that element ID exist? Specifically does it exist when this code runs? — David, Jun 08 '14 at 10:08
Judging by the `+`, `$newPostID_fromCookie` is a number. IDs should not be numbers. — Niet the Dark Absol, Jun 08 '14 at 10:09
@NiettheDarkAbsol isn't basically anything allowed in html5? — PeeHaa, Jun 08 '14 at 10:11
@PeeHaa Yes, true, numeric IDs are acceptable in HTML5. However, older browsers won't like them, and it's just a bad idea anyway because it makes it much easier to end up with duplicate IDs ;) — Niet the Dark Absol, Jun 08 '14 at 10:13
try to add console.log(document.getElementById('cookie_$newPostID_fromCookie')); — hutchbat, Jun 08 '14 at 14:35

score 0 · Answer 1 · edited May 23 '17 at 11:57

0

Your $newPostID_fromCookie seems to be an integer. In xHTML, this is not valid and maybe your browser does not like it. You should use a string (with a prefix for example):

document.getElementById('cookie_$newPostID_fromCookie').scrollIntoView();

Of course, change your HTML in consequence.

edited May 23 '17 at 11:57

Community

1
1

answered Jun 08 '14 at 10:13

Maxime Lorant

34,607
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score -1 · Answer 2 · answered Jun 08 '14 at 10:30

-1

The getElementById() does a DOM lookup and returns the first element with the specified id. In this case $newPostID_fromCookie should be an id of an existing element in the DOM.

answered Jun 08 '14 at 10:30

hutchbat

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Using PHP value in javascript - working in alert() but not getelementbyid

2 Answers2