Set JavaScript variable from PHP

Question

How I can set the JavaScript variable strUser from PHP?

I am using the following code:

<script>
function val()
{
    var e = document.getElementById("ali");
    var strUser = e.options[e.selectedIndex].text;

}
</script>
brand<select id="ali" onChange="val()">
<?php
   $brand=modsearchkhodroHelper::retrieve();
   foreach($brand as $item)
   {   
   ?>
       <option value="<?php echo $item['brand']?>" selected="<?php  $id=$item['brand']?>">
           <?php echo $item['brand']?>
       </option>
   <?php
   }
   echo "</select>";
?>

Please, read more about HTTP and the way the web works. Javascript is executed by a web browser (client side), after the page have been generated by PHP on the server side. The two never "overlap": to the PHP side, Javascript is just a bunch of text to send to the client. To transmit information from the client to the server, you need a new HTTP request, triggered by a link, a form, an Ajax call... — Pik'
– Pik', Commented Aug 12, 2013 at 14:16
selected="<?php $id=$item['brand']?>"... Shouldn't that be something along the lines of <?php echo ($id==$item['brand'])?'selected="selected"':"" ?> ? That would pre-select the item if it equals whatever is in variable $id.. — Duroth
– Duroth, Commented Aug 12, 2013 at 14:23

Joshua Dwire · Accepted Answer · 2013-08-12 14:17:26Z

19

If you want to set the variable when the page loads, you could use something like this in the PHP code:

<script type="text/javascript">var strUser = <?php echo json_encode($someVariable); ?>;</script>

Just make sure to remove the later variable declaration from the JavaScript.

If you want to set the variable after the page loads, you'll have to use an AJAX call to ge the value from the server.

answered Aug 12, 2013 at 14:17

Joshua Dwire

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6 Comments

Martijn Over a year ago

This is the wrong way arround :) This is giving some php value to javascript not javascript to php (which is harder)

Joshua Dwire Over a year ago

@Martijn From what I understood, the OP wanted to set a JavaScript variable from PHP. I think the title was wrong. I edited the question, but maybe I edited it wrong. It was fairly hard to understand.

Joshua Dwire Over a year ago

@Kneel-Before-ZOD I json_encode the variable before passing it to JavaScript to make sure everything is escaped properly if it is a string. If it's an object, then json_encode will format it as a JavaScript compatible object that can be injected directly into the JavaScript code.

Martijn Over a year ago

Hm, you might be right. Difficult question. Kinda odd, because placing phpinfo into a file with javascript is about the same as he is doing right now

Joshua Dwire Over a year ago

@Martijn Either way he meant it, we've got an answer for each way. Hopefully the OP will be back soon to clarify what he meant. Until then, you can view the original version of the question by clicking the "Edited x minutes ago" link under the question.

|

Padmanathan J · Accepted Answer · 2013-08-12 14:31:32Z

5

Use Cookie in your javascript

<script type="text/javascript">
    document.cookie = "cookieName=cookieValue";
</script>

in your php

<?php 
   $phpVar =  $_COOKIE['cookieName'];

   echo $phpVar;
?>

answered Aug 12, 2013 at 14:31

Padmanathan J

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