a little background

Wordpress has the ability to attach images to each page/post, and then display them using get_children function with some parameters to target the images.

I like to use those images as a simple slider or a static image the header, sometimes the footer, etc.

The problem i faced was if you insert any image into the post/page content, that image then becomes an attachment and therefore appears anywhere I use the get_children function.

So I wrote an anonymous shortcode, that solves my very problem. I use regex to match a word such as slider in the file name and only display those images. ie: slider_image0.jpg would show but image0.jpg would not.

the code

add_shortcode( 'slider_gallery', function( $atts ) {

    $defaults = array(
        'show_only' => 'slider',
        'img_class' => 'theImage',

    );
    extract( shortcode_atts( $defaults, $atts ) );

    $post_id = get_the_ID(); //use post id so this shortcode can be used on any page!

    $images =& get_children( 'post_parent='.$post_id.'&order=ASC&orderby=menu_order&post_type=attachment&post_mime_type=image' );

    if ( empty( $images ) ) :
    return false;
    else :

        foreach ( $images as $attachment_id => $attachment ):
        $title = $attachment->post_title;
    $imageData = wp_get_attachment_url( $attachment_id );
    preg_match( '/(.*?)('.$show_only.'.+ ?)/i', $imageData, $matches ); //match all files with 'slider' etc: slider_one.jpg or oneslider.jpg
    $media[] = @$matches[0];
    $media = array_filter( $media );
    endforeach;
    foreach ( $media as $m ):
    echo '<img class="'.$img_class.'" src="'.$m.'"/>';
    endforeach;
    endif;

    return;

} );

how to use

this will use the default parameters slider and theImage for class

[slider_gallery]

or like this with the two parameters:

[slider_gallery show_only="slider" img_class="theImage"]

which you substitue what you want only show and which class ie: gallery_image0.jpg would be:

[slider_gallery show_only="gallery"]