php: read dir with images and create style-rule with position based on filename?

I'm not much of a php junkie so I need your help in creating the best and simplest solution for this. I have a folder "path/images/headers" where I have multiple header images (all cut to the right size). The filenames look like this "something_right.jpg" , "xyz_left.jpg", "dfjakdfjs_center.jpg", etc.

I need a way to read this folder, provide a random image file and finally create a style rule that sets this image as background value and sets the background-X position开发者_开发技巧 based on the _underscore value of the filename!

<?php
    function header_image() {

        $imgDir = bloginfo('template_url'); ?>/images/headers;
        $pos = 
        return "transparent url('images/headers/" . $img . "') no-repeat " . $pos . " center;"

    }
    ?>
    <style type="text/css">
        .header-image {
            background: <?php echo header_image(); ?>
        }
    </style>

So imagine I have "xyz_right.jpg" the style rule should look like this:

background: transparent url('images/headers/xyz_right.jpg') no-repeat right center;

Any idea what's the best solution to do so?

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I'd go with glob, shuffle and preg_match, not DirectoryIterator and strpos.

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There is quite a lot to this, you need a way to point to each file (DirectoryIterator class might help here, especially the getBasename method) and a way to get the value from the file name (I would opt for strpos to search the string for each condition).

How many files are in/will be in the folder?