Question: I want to make some thing like this

**my-php-file.php**

```
  $lang = 'es';

```

**my-js-file.js**

```
if ($lang == es)
   {
   something-magical-happens;
   }

```

or like this:

```
if (URL == www.mydomain.com/index.php?lang=es)
   {
   something-magical-happens;
   }

```

Answer: 
you could generate js *on-the-fly*

my.js.php:

```
<?php echo "//Yes." ?>
var i = "<?php echo $_GET['lang']; ?>";

function doSomethingWithI(){
  alert(i);
}

```

Now, try to include

```
<script type="text/javascript" src="my.js.php?lang=es"></script>

```

in your html and you'll see :)

**Edit:** Check it in action here: <http://h.kissyour.net/so/phpjs/>

**Edit:** Edited example on my server to closer resemble what I wrote here.

**Edit:** Oh yes. **Don't forget to clean your code!**
You can – as the accepted answer indicates – generate entire javascript files with PHP. But if you are just trying to access some limited dynamic content, this is often overkill. If you are just trying to access a few variables that need to be PHP generated, inline javascript works fine. Add this to your HTML's head:

```
<script type="text/javascript">
  <?php if( $condition == true ) : ?>
    var variable1 = <?php $var1 ?>,
        variable2 = <?php $var2 ?>;
  <?php else: ?>
    var variable1 = <?php $var1Alt ?>,
        variable2 = <?php $var2Alt ?>;
  <?php endif; ?>
</script>

```

Just make sure you add this *before* any linked scripts depend on these variables.