how to integrate an external API in wordpress

Hi, maybe you can use wp_remote_request() function. reference: wp_remote_request()

I second the use of wp_remote_request() ?? It sounds like you have existing PHP code that you need to integrate into WP. One way to do so is to create a custom page template that contains your PHP code. Any output from your code becomes client side page content. You can still use cURL or whatever you already have to access the API. As a page template, you’re able to use wp_remote_request() and any other WP resources. You’ll likely want to at least call get_header() and get_footer() so your page is theme styled like other WP pages. You can also replicate your theme’s HTML structure from it’s default page.php template for further integration with the theme.
https://developer.www.ads-software.com/themes/template-files-section/page-template-files/

It’s best to keep custom page templates in a child theme so they are protected from being lost during updates.
https://developer.www.ads-software.com/themes/advanced-topics/child-themes/