Missing Argument

Question

I have the following code in my functions.php to show a lightbox on the Simple Paypal Shopping Cart Plugin

function make_wpspsc_thumbs_lightbox_previews( $thumbnail, $atts ) {

    // Code Credit: http://stackoverflow.com/questions/19323324/how-to-get-image-src-attribute-value-from-php-string

    $doc = new DOMDocument();

    // Let's make sure we don't execute this code on the wrong elements & blow up the site
    if ( ! is_object( $doc ) ) {
        return $thumbnail;
    }

    libxml_use_internal_errors(true);
    $doc->loadHTML( $thumbnail );
    $xpath = new DOMXPath($doc);
    $imgs = $xpath->query("//img");
    for ($i=0; $i < $imgs->length; $i++) {
            $img = $imgs->item($i);
            $src = $img->getAttribute("src");
    }
    // Now let's use the image src we just got & rel="lightbox" because that's what Responsive Lightbox from dFactory uses
    $new_thumbnail = '<a href="'.$src.'" rel="lightbox">'.$thumbnail.'</a>';

    return $new_thumbnail;
}
add_filter( 'wspsc_product_box_thumbnail_code', 'make_wpspsc_thumbs_lightbox_previews' );

When I add something the the cart I get the warning:

Warning: Missing argument 2 for make_wpspsc_thumbs_lightbox_previews()

On line 16 which is this:

function make_wpspsc_thumbs_lightbox_previews( $thumbnail, $atts ) {

Can anyone see what is causing the problem please?

Answer 1

You didn't specify how many arguments your function accepts when you used add_filter:

add_filter( $tag, $function_to_add, $priority, $accepted_args );

Your code only passes a $tag and a $function_to_add, but it doesn't tell WordPress what priority it should be, or how many accepted arguments your function takes. You need to fix that. If you don't provide the 4th parameter, WordPress assumes your function only accepts 1 argument, even if you define 2 in your function ( $thumbnail and $atts ).

Also, if the filter only provides a single argument, then WordPress can't pull a second argument out of thin air