Fatal error: Cannot redeclare function

Question

I have multiple php scripts that sits in mu-plugins folder to help redirect traffic. The php script is shown below and each script just differs in terms on the page ID eg. is_page( 90 ) for the first script and is_page( 50 ) for another script. However, I get the following error message

Fatal error: Cannot redeclare geoip_redirect() (previously declared in /home/server1/public_html/wp-content/mu-plugins/GeoIPDetecti‌​onv 76.php:6) in /home/server1/public_html/wp-content/mu-plugins/GeoIPDetecti‌​onv 90.php on line 43

May I know how to resolve this error? I tried include the declaration portion in core.php (shown at bottom of post) and getting each script to include it only once (using include_once) but am still getting the error. Thank you.

Main script

<?php /* Template Name: GeoIPDetectionv3 */

include_once 'core.php';

function geoip_redirect(){
    if ( is_admin() ) {
        return; // Not applicable.
    }
    if ( 123 !== get_current_blog_id() ) {
        return; // Not on blog ID 123.
    }
    if ( ! is_page( 90 ) ) {
        return; // Not a specific page ID on this blog.
    }
    if ( ! function_exists( 'geoip_detect2_get_info_from_current_ip' ) ) {
        return;
    }

    $userInfo    = geoip_detect2_get_info_from_current_ip();
    $countryCode = $userInfo->country->isoCode;

    switch ($countryCode) {
        case 'DE':
            $redirect_to = '/germany';
            break;
        case 'US':
            $redirect_to = '/usa';
            break;
        case 'SG':
            $redirect_to = 'www.google.com.sg';
            break;
        default:
            $redirect_to = 'www.google.com.sg';
    }
    if ( ! empty( $redirect_to ) ) {
        if ( stripos( $redirect_to, 'http' ) === 0 ) {
            wp_redirect( $redirect_to ); // Full URL.
        } else {
            wp_redirect( home_url( $redirect_to ) ); // Local /path.
        }
        exit;
    }
}

Core.php

<?php /* Template Name: GeoIPDetectionv3 */

add_action('template_redirect', 'geoip_redirect', 5);

Answer 1

This is the example code to fix the fatal error and redirect user as per the given page id. You can further optimise the code, if the redirection is going to remain same for "DE" and "US" for all the pages, you can just skip the if ( is_page( 90 ) ) check for these country codes.

add_action( 'template_redirect', 'geoip_redirect', 5 );

function geoip_redirect() {

    //Return if not admin, or the blog id is not 123, or not on the specified page, or if the function doesn't exists
    //List of pages to redirect from
    $pages = array(
        50,
        90
    );
    //Return if not admin, or the blog id is not 123, or not on the specified page, or if the function doesn't exists
    if ( is_admin() || 123 !== get_current_blog_id() || ! is_page( $pages ) || ! function_exists( 'geoip_detect2_get_info_from_current_ip' ) ) {
        return;
    }

    $userInfo    = geoip_detect2_get_info_from_current_ip();
    $countryCode = $userInfo->country->isoCode;

    if ( is_page( 90 ) ) {
        switch ( $countryCode ) {
            case 'DE':
                $redirect_to = '/germany';
                break;
            case 'US':
                $redirect_to = '/usa';
                break;
            case 'SG':
                $redirect_to = 'www.google.com.sg';
                break;
            default:
                $redirect_to = 'www.google.com.sg';
        }
    } elseif ( is_page( 50 ) ) {
        //Change URL accordingly
        switch ( $countryCode ) {
            case 'DE':
                $redirect_to = '/germany';
                break;
            case 'US':
                $redirect_to = '/usa';
                break;
            case 'SG':
                $redirect_to = 'www.amazon.com.sg';
                break;
            default:
                $redirect_to = 'www.amazon.com.sg';
        }
        //So on you can add additional else if conditions for rest of your pages
    }

    if ( ! empty( $redirect_to ) ) {
        if ( stripos( $redirect_to, 'http' ) === 0 ) {
            wp_redirect( $redirect_to ); // Full URL.
        } else {
            wp_redirect( home_url( $redirect_to ) ); // Local /path.
        }
        exit;
    }
}

This code is suitable if redirection is gonna remain same for "US" and "DE"

add_action( 'template_redirect', 'geoip_redirect', 5 );

function geoip_redirect() {

    //List of pages to redirect from
    $pages = array(
        50,
        90
    );
    //Return if not admin, or the blog id is not 123, or not on the specified page, or if the function doesn't exists
    if ( is_admin() || 123 !== get_current_blog_id() || ! is_page( $pages ) || ! function_exists( 'geoip_detect2_get_info_from_current_ip' ) ) {
        return;
    }

    $userInfo    = geoip_detect2_get_info_from_current_ip();
    $countryCode = $userInfo->country->isoCode;

    if ( in_array( $countryCode, array( "US", "DE" ) ) ) {
        $redirect_to = 'US' == $countryCode ? '/usa' : '/germany';
    } else {
        if ( is_page( 90 ) ) {
            switch ( $countryCode ) {
                case 'SG':
                    $redirect_to = 'www.google.com.sg';
                    break;
                default:
                    $redirect_to = 'www.google.com.sg';
            }
        } elseif ( is_page( 50 ) ) {
            //Change URL accordingly
            switch ( $countryCode ) {
                case 'SG':
                    $redirect_to = 'www.amazon.com.sg';
                    break;
                default:
                    $redirect_to = 'www.amazon.com.sg';
            }
        }
    }
    if ( ! empty( $redirect_to ) ) {
        if ( stripos( $redirect_to, 'http' ) === 0 ) {
            wp_redirect( $redirect_to ); // Full URL.
        } else {
            wp_redirect( home_url( $redirect_to ) ); // Local /path.
        }
        exit;
    }
}

Well, you can further optimise the code, depending upon what are the redirection values for your 15 pages, if it's all similar you can definitely come up with ways to minimise the code.