I occasionally come across pages where some Javascript is included via a PHP file:
<html>
<head>
<script type="text/javascript" src="fake_js.php"></script>
</head>
<body onload="handleLoad();">
</body>
</html>
where the contents of fake_js.php might look something like this:
<?php header('Content-type: text/javascript') ?>
function handleLoad() {
alert('I loaded');
}
What are the advantages (or disadvantages) to including Javascript like this?
There's no benefit for the example you gave above (beyond peculiar deployment scenarios where you have access to .php files and not .js files, which would be insane but not unheard of).
That said, this approach allows you to pass the JS through the php parser - which means you can generate your JS dynamically based on server variables.
It makes it easy to set javascript variables from the server side.
var foo = <?=$foo?>
I usually have one php/javascript file in my projects that I use define any variables that need to be used in javascript. That way I can access constants used on the server-side (css colors, non-sensitive site properties, etc) easily in javascript.
Edit: For example here's a copy of my config.js.php file from the project I'm currently working on.
<?php
require_once "libs/config.php";
if (!function_exists("json_encode")) {
require_once "libs/JSON.php";
}
header("Content-type: text/javascript");
echo "var COLORS = ". json_encode($CSS_COLORS) .";\n";
echo "var DEBUG = ". ((DEBUG == true) ? "true" : "false").";";
?>
Advantage (not PHP specific - I used this technique in EmbPerl and JSP) would be the ability to dynamically generate or tweak/customize the JavaScript code on the server side.
An example usage would be population of an array based on the contents of a DB table. Or application of localization techniques.
seamless version control without the need to modify client templates
<script src='script.php'></script>
<?php
include('correct_script');
?>
If you don't need it, don't use it:
The first thing you need to keep in mind is YAGNI. You Ain't Gonna Need It. Until a certain feature, principle, or guideline becomes useful and relevant, don't use it.
Disadvantages:
Advantages:
<head> </head> section of the HTMLUnless the javascript is truely unique (i.e. JSON, parameters/variables) you don't gain much. But in every case you should minimize the amount of JS generated on the server side and maximize the amount of code in the static files. Don't forget that if it's dynamic, it has to be generated/downloaded again and again so it's not wanted for it to be a heavy process.
Also:
Agree with tj111. Apart from what tj mentioned, I also found php-generated javascripts a great weapon to fight the browser's caching tricks. Not that long ago I was cursing the whole javascript for its being constantly cached by the browser. Refreshing the page helped me not, had to clear the whole cache in order to force the browser to reload the javascript files. As soon as I built a php wall in front of my javascripts:
fake_js.php:
<?php
header('Content-type: text/javascript')
include('the_real_javascript.js');
?>
A fresh new javascript would always show up at the client side. However this approach is obviously only good in the development phase, when it can save the developer quite some headache to have the correct javascript loaded in the browser. Of course when connecting to localhost, the penalty of repeatedly loading the same file is not as big.
In a live web application/site client-side caching is welcome to reduce network traffic and overall server load.
If you don't have full server access and can't turn on gzip encoding then it's pretty useful to put the following in your javascript file (note: will need to be renamed to file.js.php or parsed as PHP through .htaccess directive):
<?php
ob_start( 'ob_gzhandler' );
header("Content-type: text/javascript");
?>
// put all your regular javascript below...
You could also use it for better cache control, visitor tracking, etc in lieu of server-controlled solutions.
Absolutely none, IMHO. I use a js framework that I wrote to handle the setting of whatever server-side variables I need to have access to. It is essentially the same as embedding PHP in JavaScript, but much less ambiguous. Using this method allows you to also completely separate server-side logic and html away from javascript. This results in much cleaner, more organized and lowly-coupled modular code.
You could do something like this in your html:
<script type="text/javascript">
registry = {
myString : '<?php echo $somePhpString; ?>',
myInt : <?php echo $somePhpInteger; ?>
}
</script>
And then do something like this in your js:
if (registry.myInt === 1) {
alert(registry.myString);
}