Insert this code into the functions.php file within your WordPress child-theme to inject any custom code into the HEADER area of a specific page on your WordPress website.

wordpress-header-specific-page-hook.php

<?php

// Inserting Header Script on Specific Page with WordPress
// https://endurtech.com/insert-script-into-wordpress-header/

add_action( 'wp_head', 'custom_header_page_scripts', 2 );
function custom_header_page_scripts()
{
  if( is_page( 123 ) ) //set page number to your page number
  {
    echo '<script>alert( "This script is triggered within the header of page-id 123 on your website." );</script>';
  }
}

// Alternatively, you can stop and restart PHP processing to inject your code
// which helps bypass potential issues with apostrophes or quotations
add_action( 'wp_head', 'custom_header_page_scripts', 2 );
function custom_header_page_scripts()
{
  if( is_page( 197 ) ) // change the target page number (197) to your desired target page number
  {
	?>
<script>alert( "This script is triggered from within the header of page-id 123 on your website." );</script>
	<?php
  }
}

?>