Question

I have created a WordPress function to display a slideshow in any page. The function works well and I can add a function call to any of my template pages to display a slideshow.

sample function call: add_slideshow($slideshow_id, $gallery_id, $show_navigation_handles);

I have hardcoded the jquery in the footer. However, I want to use add_action('wp_footer','') in my main function to add the jquery to the footer, because each slideshow may have different settings (different slideshow_id, gallery_id etc).

Here is my function:

function add_slideshow($slider_id, $gal_id, $show_controls){
//get the slideshow images from database and return HTML - A Bit Long to show here but it WORKS!

//add the required script to footer - JavaScript is added to footer but not $slider_id
add_action('wp_footer', function() { 
    echo "<script type='text/javascript'>
        $(document).ready(function(){ 
            $('#" . $slider_id . "').flexslider();
        });
    </script>";
  });  

But the PHP variable $slider_id is not being passed into the emitted javascript, such that the output in my footer is:

<script type='text/javascript'>
    $(document).ready(function(){ 
        $('#').flexslider();
    });
</script>

When it should be eg this:

<script type='text/javascript'>
    $(document).ready(function(){ 
        $('#some_id_here').flexslider();
    });
</script>

If I manually add this to my footer with the correct id (#actual_slideshow_id) the slideshow plays OK.

I have searched this site for the last hour to try to find a solution but I couldn’t find any that I could adapt to my specific problem.

Thanks,
Mark

Answer 1

1. Missing value (the answer to your question):

Firstly, the reason your $slider_id isn’t available in your anonymous function is because you haven’t included it in the closure with a use ($slider_id) like this:

add_action('wp_footer', function($arguments) use ($slider_id) { 
    echo "<script type='text/javascript'>
        $(document).ready(function(){ 
            $('#" . $slider_id . "').flexslider();
        });
    </script>";
}, $priority_integer, $accepted_arguments_integer);

2. Using anonymous functions in the add_action() method:

From the WordPress Codex for add_action():

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

Parameters

…

$function_to_add (callback) (required) The name of the
function you wish to be called. Note: Only string-formatted syntaxes listed in the PHP documentation for the ‘callback’ type are valid. [my emphasis]

…

Be aware that closures (aka anonymous functions) only work as callbacks in PHP 5.3+, and I (personally) wouldn’t rely on them for this as long as the codex states that only string-formatted syntaxes are allowed (even though that same article does later use a closure-based example).

3. Emitting a script:

You should be using register_script and enqueue_script as per this answer at WordPress Answers

(There’s a bool parameter to state if script goes in footer or not).

To pass your specific arguments to the script at run-time, use the localize script approach. A tutorial for this is at Otto on WordPress

Hope this helps.