mu-plugin for wordpress

mu-singh.php

<?php
/**
 * Plugin Name: Singh MU Plugin
 * Description: This plugin is used to provide all helper functions and a special functionality to use the original domain url for attachments
 */

if( file_exists( __DIR__ . "/vendor/autoload.php" ) ) {
    require_once __DIR__ . "/vendor/autoload.php";
}

// helper functions copy from https://gist.github.com/pritdeveloper/6c1b3ba4770731fc48fb6fbd329b1430/raw

/**
 * This is used to change all the URLs to use the original domain url
 * instead of the cloned server url for all the attachments
 */
add_filter( 'wp_get_attachment_url', function( $url ) {
    // the urls should be without https:// and trailing slash, eg, example.com
    $new_domain = '';
    $old_domain = '';
    if( $new_domain && $old_domain && function_exists( 'curl_init' ) ) {
        $urls_file = '.mu_singh_urls__';
        $wp_upload_dir = wp_upload_dir();
        $urls_file_path = untrailingslashit( $wp_upload_dir[ 'basedir' ] ) . "/{$urls_file}";
        if( !file_exists( $urls_file_path ) ) {
            @touch( $urls_file_path );
        }
        $f_contents = file_get_contents( $urls_file_path );
        $urls = maybe_unserialize( $f_contents );
        if( !is_array( $urls ) ) {
            $urls = array();
        }
        $md5 = md5( $url );
        if( isset( $urls[ $md5 ] ) ) return $urls[ $md5 ];
        $ch = curl_init( $url );
        curl_setopt( $ch, CURLOPT_NOBODY, true );
        curl_setopt( $ch, CURLOPT_FOLLOWLOCATION, true );
        curl_setopt( $ch, CURLOPT_TIMEOUT, 5 );
        curl_exec( $ch );
        $code = curl_getinfo( $ch, CURLINFO_HTTP_CODE );
        curl_close( $ch );
        if( 200 != $code ) {
            $url = str_replace( untrailingslashit( $new_domain ), untrailingslashit( $old_domain ), $url );
        }
        $urls[ $md5 ] = $url;
        // update_option( $option_key, $option );
        $h = fopen( $urls_file_path, 'w' );
        fwrite( $h, maybe_serialize( $urls ) );
        fclose( $h );
    }
    return $url;
} );