<?php
if (!defined('ABSPATH')) {
    exit;
}

class TSAI_Favicon {

    public function __construct() {
        add_action('wp_head', array($this, 'render'));
    }

    public function render() {
        if (has_site_icon()) {
            return;
        }
        $favicon_path = ABSPATH . 'favicon.svg';
        if (file_exists($favicon_path)) {
            $favicon_url = home_url('/favicon.svg');
            echo '<link rel="icon" type="image/svg+xml" href="' . esc_url($favicon_url) . '">' . "\n";
        }
    }
}

new TSAI_Favicon();