Load CSS files using PHP, based on page content

Is this possible? For example, I'm loading all of my css files through my header. One of the things I'm using is the JQuery DataTables plug-in. However, I don't want to load the DataTables css unless the page content contains a DOM element of type "table". I've tried evaluating the page with:

file_get_contents($_SERVER["PHP_SELF"];

Which doesn't work. What's the most efficient way to evaluate开发者_C百科 your page's content in PHP, and load CSS files appropriately? Or, is javascript a better way to do this?

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I would say you're over thinking this. Set a far away cache expiration date on your DataTable css and simply let the user cache the css file.

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This could be done using output buffering, but it sounds like a bad idea to collect the whole document, analyze it, and then add a style sheet header - it's likely to be slow, kludgy and may even hit memory limits in the case of huge tables.

I would tend to say always load the CSS files, and see to it that they're properly cached.

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I found it easiest to just set some flags in my parent .php file and have the header file check for those flags and modify output as it gets loaded.

index.php:

<?php
    $INCLUDE_TABLE_CSS = true;
    include('header.php');

header.php:

blah blah blah 
<?php if (isset($INCLUDE_TABLE_CSS) && $INCLUDE_TABLE_CSS) { ?>
   <link rel="stylesheet" .... href="table.css" />
<? } ?>
blah blah blah 

Unless you've got a large number of conditional settings, then this is fairly simple to manage.

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Javascript is a better way to do this. You can do a deferred inclusion, sometimes called "lazy load". Within domready, you would check for the presence of a given class, let's say dataTable. If there are any elements with this class, you inject a new <script> or <link> tag into the header with a reference to the javascript or css file containing the needed script/styles. The <script>/<link> tag's onload event will be the callback to trigger whatever initialization you have to do once the script is in place.

My apologies that I can't tell you the jQuery way (I am a Mootools guy), but in Mootools there is a class called Asset that manages the creation of the <script>/<link> tag and the resulting onComplete event. I'm certain there is a jQuery analog to this.

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Use jQuery! This code looks to see if there is a <table>...</table> object, and if there is, it creates a new <link> element with your desired CSS file and adds it to the header object.

if ($('table').length>0){
    var link = $("<link>");
    link.attr({type: 'text/css', rel: 'stylesheet', href: 'tableStyleSheet.css'});
    $("head").append( link ); 
}