What's the easiest way to insert a global site tag on a WordPress site?

• I'm being asked to insert a global site tag {gtag('config', 'AW-xxxxxxxxxxxx');} into the Thank You page of a client's site by the Google Digital Account Exec. This is a WordPress site built by others. I attempted to insert this into the functions.php file (that seems easiest), and got an error when doing so:

  Your PHP code changes were rolled back due 
  to an error on line 45 of file
  wp-content/themes/ipropads/functions.php.
  Please fix and try saving again.
  
  Uncaught Error: Call to undefined function gtag() 
  in wp-content/themes/ipropads/functions.php:45
  Stack trace:
  #0 wp-settings.php(426): include()
  #1 wp-config.php(95): require_once('/users/ipropads...')
  #2 wp-load.php(37): require_once('/users/ipropads...')
  #3 wp-admin/admin.php(31): require_once('/users/ipropads...')
  #4 wp-admin/theme-editor.php(10): require_once('/users/ipropads...')
  #5 {main}
  thrown
  

  Can you give me a hint on the easiest way to accomplish this?

Answer:

The easiest way to do this is to add the SOGO Header Footer plugin - https://wordpress.org/plugins/oh-add-script-header-footer/

This plugin lets you add custom code into an individual page on a WordPress site. It's great for adding page specific items like Structured Data markup, Javascript, or tracking codes - like you're wanting to. To use it just:

• Login to the backend of the WordPress site and navigate to the Plugins > Add New page.
• Use the Add New button at the top of the page to search out and add the SOGO plugin.
• Once activated, you'll find two new SOGO editing sections (header and footer) at the bottom of every page WordPress editor interface.
• Paste the tracking code in the SOGO header field of the Thank You page, hit Update on the entire page and you're good to go.

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