WordPress | Get the ID of the first page using a specific template

id_via_template_name.php

<?php
// Get the ID of the first page using a specific template
function page_id_from_template( $template_name ) {
    $args = array(
        'post_type' => 'page',
        'fields' => 'ids',
        'nopaging' => true,
        'meta_key' => '_wp_page_template',
        'meta_value' => $template_name
    );
    $template_pages = get_posts( $args );
    if( $template_pages ) {
        $first_id = reset($template_pages);
        return $first_id;
    } else {
        return null;
    }
}
?>

ID of first page using a specific template

I'm using this where my contact page uses a specific template. No other pages will be using the same template. I can then grab fields from that page simply by identifying the template it uses, this means the page title or ID can vary without there being an issue.

To use this, add it to your functions.php page.

Then use it where you need it like so:

$contact_page_id = page_id_from_template( 'contact-page.php' );
echo '<p>ID of page using the contact template is:' . $contact_page_id . '</p>';

if you want a function that goes the whole way and returns a URL, try this one.