I'm trying to add a custom image setting to a custom panel/section for the header.

In functions.php, I used:

$wp_customize->add_control(new WP_Customize_Upload_Control($wp_customize,'swag_header_logo',array(
     'label'      => __('Logo', 'frontend-theme'),
     'section'    => 'swag_header_content_section',
     'settings'   => 'swag_header_logo'

Which shows up and seems to work in the customizer. However, when trying to get it to show up in the header, it gives the error:

Fatal error : Call to undefined function swag_header_logo() in /home/xxxxxx/public_html/wp-content/themes/frontend-theme/header.php on line 551

The code I used in the header.php:

$swag_header_logo = get_theme_mod('swag_header_logo');


<?php swag_header_logo(); ?>

How do I fix the error?

1 Answer 1


First part of your code looks correct - it's hard to say if it will work, because it's only part of it, but there is nothing wrong with the part you've shown.

Problem lies in this line:

<?php swag_header_logo(); ?>

You haven't defined such function anywhere in your code, so you can't call it - and that's what the error is saying ("Call to undefined function swag_header_logo()").

So how to fix it?

In this line:

$swag_header_logo = get_theme_mod('swag_header_logo');

you get the ID of attachment set as swag_header_logo and you store this ID in $swag_header_logo variable.

So if you want to display the image, just use:

echo wp_get_attachment_image( $swag_header_logo, '<SIZE>' ); // change size to real value

or if you want only the URL of the image:

echo wp_get_attachment_image_url( $swag_header_logo, '<SIZE>' ); // change size to real value
  • Didn't work for me, url just comes up (unknown)
    – Xarcell
    May 5, 2019 at 12:56
  • You say the first part of code is missing some, what is it missing?
    – Xarcell
    May 5, 2019 at 13:07
  • this seems to work: echo esc_url(get_theme_mod('swag_header_logo'));
    – Xarcell
    May 5, 2019 at 13:14
  • 1
    It all depends what exactly do you store in that option and how do you process it. May 5, 2019 at 13:35

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