Pass PHP variable to Javascript at a specific point

Question

I am passing a PHP variable to Javascript, but only at a specific point in the code. As the PHP code continues, the variable I need changes. I could easily just run the Javascript and grab the PHP variable when the page is done loading, but that won't pass the information I want. I want the Javascript to grab the PHP variable at that point, and then ignore subsequent changes to it.

The actual program I'm working with is several thousand lines of code, so I created a simple page to mess around with this issue. The code below shows what I'm trying to do.

<?php
$php_var = 'something';
if(true) {
    $php_var = 'new';
    echo ' 
        <script type="text/javascript"> 
            js_var="<?php echo $php_var; ?>"; 
            alert(js_var);
        </script>
    ';
}
$php_var = 'later changes';
?>

<script type="text/javascript">
    var js_var;
</script>

This doesn't work, however. js_var is set when the inline script is run, but it is just set to a string that says <?php echo $php_var; ?> rather than actually evaluating it.

that's because the <?php echo $php; ?> is extra and single quote strings don't process variables. try echo ("<script>js_var=$phpvar;alert(js_var);</script>"); — Youn Elan
– Youn Elan, Commented Mar 27, 2013 at 1:05

Niet the Dark Absol · Accepted Answer · 2013-03-27 00:59:30Z

2

PHP runs first, and whatever JS is sent to the browser is run. I think you just want this:

echo '<script type="text/javascript">
    js_var = '.json_encode($php_var).';
    alert(js_var);
</script>';

answered Mar 27, 2013 at 0:59

Niet the Dark Absol

326k86 gold badges480 silver badges604 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Steve Over a year ago

Yep. That does it. Thanks!

Spencer Lockhart · Accepted Answer · 2013-03-27 00:59:58Z

1

$php_var = "foo";
echo ' 
    <script> 
        var js_var = '. json_encode($php_var) .'; 
        alert(js_var);
    </script>
';

Produces:

<script>
var js_var = "foo";
alert(js_var);
</script>

answered Mar 27, 2013 at 0:59

Spencer Lockhart

1,1747 silver badges7 bronze badges

Collectives™ on Stack Overflow

Pass PHP variable to Javascript at a specific point

2 Answers 2

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related