MillennialDIYer/plugin.php

## plugin.php
<?php
/*
Plugin Name: Fallback Domain Redirect with UTM
Plugin URI:  N/A
Description: This plugin wildcard redirects to a fallback domain in case there isn't a match for your short URL.
             This would allow the short domain to be used as an alternative for any existing URL of the fallack domain.
                  - Does not work installed in a subfolder
Version:     0.4
Author:      MVS12
Author URI:  https://xyzpolr.tk
*/

// Die if no direct call to stop external access to file
if( !defined( 'YOURLS_ABSPATH' ) ) die();

// Save URI present in yourls-loader.php
yourls_add_action( 'pre_load_template' , 'fdr_save_uri' );
function fdr_save_uri()
    {
    // Start session to conserve variable across pages
    session_start();
    $fdr_loader_uri =  yourls_get_request();
    $_SESSION['fdr_loader_uri'] = $fdr_loader_uri;
    }


// Run fdr_fallback_dom function if the keyword is not found
yourls_add_action( 'redirect_keyword_not_found', 'fdr_fallback_dom' );

// Run fdr_fallback_dom function if the loader fails to load due to extraordinary characters
yourls_add_action( 'loader_failed', 'fdr_fallback_dom' );

// fdr_fallback_dom is the function that redirecs the
function fdr_fallback_dom()
    {
    // Check if the plugin is activce and if so, perform the redirect
    if( yourls_is_active_plugin( 'fallback-domain-redirect-w-utm/plugin.php' ) )
        {
        // Start the session to retreive fdr_loader_uri variable later
        session_start();

        // Get values from the database
        $fallback_dom = yourls_get_option( 'fallback_dom' );
        $fdr_utm_source = yourls_get_option( 'fdr_utm_source' );

        // Retreive fdr_loader_uri variable via the session
        $mod_url = $_SESSION['fdr_loader_uri'];

        // Remove existing UTM Parameters
        $mod_url = preg_replace( '/&?utm_.+?(&|$)$/', '', $mod_url );

        // Append the initial request plus UTM Parameter to the fallback domain
        $fallback_dom_ext = $fallback_dom.$mod_url.$fdr_utm_source;

        // Redirect to the fallback domain
        yourls_redirect( $fallback_dom_ext, 307 ); //Use a temporal redirect in case there is a valid keyword in the future
        }
    }


// Register plugin config page
yourls_add_action( 'plugins_loaded', 'fdr_config_add_page' );
function fdr_config_add_page()
    {
    // parameters: page slug, page title, and function that will display the page itself
    yourls_register_plugin_page( 'fallback_url_config', 'Fallback Domain Redirect with UTM Plugin Config', 'fdr_config_do_page' );
    }

// Display Plugin Configuration Page
function fdr_config_do_page()
    {

    // Submit form
    fdr_config_update_option();

    // Get values from the database
    $fallback_dom = yourls_get_option( 'fallback_dom' );
    $fdr_utm_source = yourls_get_option( 'fdr_utm_source' );

    // Remove "?utm_source=" from utm_source if applicable
    $fdr_utm_source = str_replace("?utm_source=" , "", $fdr_utm_source);

    echo <<<HTML
    <h2>Fallback Domain Redirect with UTM Plugin Configuration</h2>
    <hr>
    <h3>Fallback Domain</h3>
    <p>Here you can configure the Domain to wildcard-redirect to, in case the keyword is not found in database.</p>
    <form method="post">
    <p><label for="fallback_dom">Domain to wildcard redirect to</label> <input type="text" id="fallback_dom" name="fallback_dom" value="$fallback_dom" size="40" /></p>
    <p><strong>Note</strong> - Please include protocol and closing slash. For example: <strong>https://</strong>example.com<strong>/</strong> </p>
    <hr>
    <h3>UTM Source Parameter - Optional</h3>
    <p>The following UTM parameter's primary purpose is added information in <a href="https://support.google.com/analytics/answer/1033863#parameters">Google Analytics</a>. Its use is optional.</p>
    <p>Keep in mind that UTM parameters are case-sensitive. Lowercase letters and hyphens for spaces are recommended.</p>
    <p><label for="fdr_utm_source">utm_source=</label> <input type="text" id="fdr_utm_source" name="fdr_utm_source" value="$fdr_utm_source" size="40" /></p>
    <hr>
    <p><input type="submit" value="Update values" /></p>
    </form>
HTML;
    }

// Update fallback domain configuration in database
function fdr_config_update_option()
    {
        $in1 = $_POST['fallback_dom'];

        if( $in1 )
            {   // Performs validation of fallback domain.

                // To assure the domain ends in a '/', it is stripped if applicable and added.
                rtrim($in1,"/").'/';

                // Gets string value of variable
                $in1 = strval( $in1);

                // Update value in database
                yourls_update_option( 'fallback_dom', $in1 );
            }

        $in2 = $_POST['fdr_utm_source'];

        if ( $in2 )
            {
                // Performs validation on the utm_source parameter.

                // Gets string value of variable
                $in2 = strval( $in2);

                if ( $in2 != "")
                {
                    // Adds utm_source prefix
                    $in2 = '?utm_source='.$in2;

                    // Update value in database
                    yourls_update_option( 'fdr_utm_source', $in2 );
                }
                elseif ( $in2 == "")
                {
                    // Update value in database
                    yourls_update_option( 'fdr_utm_source', $in2 );
                }
            }
    }


// PHP tag left unclosed
	<?php
	/*
	Plugin Name: Fallback Domain Redirect with UTM
	Plugin URI: N/A
	Description: This plugin wildcard redirects to a fallback domain in case there isn't a match for your short URL.
	This would allow the short domain to be used as an alternative for any existing URL of the fallack domain.
	- Does not work installed in a subfolder
	Version: 0.4
	Author: MVS12
	Author URI: https://xyzpolr.tk
	*/

	// Die if no direct call to stop external access to file
	if( !defined( 'YOURLS_ABSPATH' ) ) die();

	// Save URI present in yourls-loader.php
	yourls_add_action( 'pre_load_template' , 'fdr_save_uri' );
	function fdr_save_uri()
	{
	// Start session to conserve variable across pages
	session_start();
	$fdr_loader_uri = yourls_get_request();
	$_SESSION['fdr_loader_uri'] = $fdr_loader_uri;
	}


	// Run fdr_fallback_dom function if the keyword is not found
	yourls_add_action( 'redirect_keyword_not_found', 'fdr_fallback_dom' );

	// Run fdr_fallback_dom function if the loader fails to load due to extraordinary characters
	yourls_add_action( 'loader_failed', 'fdr_fallback_dom' );

	// fdr_fallback_dom is the function that redirecs the
	function fdr_fallback_dom()
	{
	// Check if the plugin is activce and if so, perform the redirect
	if( yourls_is_active_plugin( 'fallback-domain-redirect-w-utm/plugin.php' ) )
	{
	// Start the session to retreive fdr_loader_uri variable later
	session_start();

	// Get values from the database
	$fallback_dom = yourls_get_option( 'fallback_dom' );
	$fdr_utm_source = yourls_get_option( 'fdr_utm_source' );

	// Retreive fdr_loader_uri variable via the session
	$mod_url = $_SESSION['fdr_loader_uri'];

	// Remove existing UTM Parameters
	$mod_url = preg_replace( '/&?utm_.+?(&\|$)$/', '', $mod_url );

	// Append the initial request plus UTM Parameter to the fallback domain
	$fallback_dom_ext = $fallback_dom.$mod_url.$fdr_utm_source;

	// Redirect to the fallback domain
	yourls_redirect( $fallback_dom_ext, 307 ); //Use a temporal redirect in case there is a valid keyword in the future
	}
	}


	// Register plugin config page
	yourls_add_action( 'plugins_loaded', 'fdr_config_add_page' );
	function fdr_config_add_page()
	{
	// parameters: page slug, page title, and function that will display the page itself
	yourls_register_plugin_page( 'fallback_url_config', 'Fallback Domain Redirect with UTM Plugin Config', 'fdr_config_do_page' );
	}

	// Display Plugin Configuration Page
	function fdr_config_do_page()
	{

	// Submit form
	fdr_config_update_option();

	// Get values from the database
	$fallback_dom = yourls_get_option( 'fallback_dom' );
	$fdr_utm_source = yourls_get_option( 'fdr_utm_source' );

	// Remove "?utm_source=" from utm_source if applicable
	$fdr_utm_source = str_replace("?utm_source=" , "", $fdr_utm_source);

	echo <<<HTML
	<h2>Fallback Domain Redirect with UTM Plugin Configuration</h2>
	<hr>
	<h3>Fallback Domain</h3>
	<p>Here you can configure the Domain to wildcard-redirect to, in case the keyword is not found in database.</p>
	<form method="post">
	<p><label for="fallback_dom">Domain to wildcard redirect to</label> <input type="text" id="fallback_dom" name="fallback_dom" value="$fallback_dom" size="40" /></p>
	<p><strong>Note</strong> - Please include protocol and closing slash. For example: <strong>https://</strong>example.com<strong>/</strong> </p>
	<hr>
	<h3>UTM Source Parameter - Optional</h3>
	<p>The following UTM parameter's primary purpose is added information in <a href="https://support.google.com/analytics/answer/1033863#parameters">Google Analytics</a>. Its use is optional.</p>
	<p>Keep in mind that UTM parameters are case-sensitive. Lowercase letters and hyphens for spaces are recommended.</p>
	<p><label for="fdr_utm_source">utm_source=</label> <input type="text" id="fdr_utm_source" name="fdr_utm_source" value="$fdr_utm_source" size="40" /></p>
	<hr>
	<p><input type="submit" value="Update values" /></p>
	</form>
	HTML;
	}

	// Update fallback domain configuration in database
	function fdr_config_update_option()
	{
	$in1 = $_POST['fallback_dom'];

	if( $in1 )
	{ // Performs validation of fallback domain.

	// To assure the domain ends in a '/', it is stripped if applicable and added.
	rtrim($in1,"/").'/';

	// Gets string value of variable
	$in1 = strval( $in1);

	// Update value in database
	yourls_update_option( 'fallback_dom', $in1 );
	}

	$in2 = $_POST['fdr_utm_source'];

	if ( $in2 )
	{
	// Performs validation on the utm_source parameter.

	// Gets string value of variable
	$in2 = strval( $in2);

	if ( $in2 != "")
	{
	// Adds utm_source prefix
	$in2 = '?utm_source='.$in2;

	// Update value in database
	yourls_update_option( 'fdr_utm_source', $in2 );
	}
	elseif ( $in2 == "")
	{
	// Update value in database
	yourls_update_option( 'fdr_utm_source', $in2 );
	}
	}
	}


	// PHP tag left unclosed