plugin.php

<?php
/*
Plugin Name: Force Allow Duplicate URLs
Plugin URI: https://github.com/kesslerio/yourls-force-allow-duplicates
Description: Truly allows creating multiple short URLs (with different keywords) for the same destination URL
Version: 1.0.0
Author: Martin Kessler
Author URI: https://github.com/kesslerio
*/

// Block direct calls
if (!defined('YOURLS_ABSPATH')) die();

// Hook into the URL exists filter when the force parameter is present
yourls_add_filter('url_exists', 'force_allow_duplicates', 10, 1);

// Hook into the 'add new URL' function to bypass unique URL checking
yourls_add_filter('shunt_add_new_link', 'force_add_duplicate_url', 10, 4);

// Also keep the original allow_existing_urls filter as a fallback
yourls_add_filter('add_new_link_already_stored_filter', 'force_allow_existing_urls');

/**
 * Bypass the unique URL check when 'force=1' is set in the request
 * 
 * @param bool $url_exists Whether the URL exists in the database
 * @return bool False if force=1 is set, original value otherwise
 */
function force_allow_duplicates($url_exists) {
    // Check if we have the force parameter set to 1
    if (isset($_REQUEST['force']) && $_REQUEST['force'] == '1') {
        // Return false to indicate URL doesn't exist, allowing a new short URL to be created
        return false;
    }
    
    // Return original value otherwise
    return $url_exists;
}

/**
 * Force add a new URL if the 'force' parameter is set
 * This bypasses the normal add_new_link function when needed
 * 
 * @param mixed $pre Default value to return
 * @param string $url URL to shorten
 * @param string $keyword Optional keyword
 * @param string $title Optional title
 * @return mixed False if force parameter is not present, or the result of the add operation
 */
function force_add_duplicate_url($pre, $url, $keyword, $title) {
    global $ydb;
    
    // Only execute if force=1 is set and we're dealing with a duplicate URL
    if (isset($_REQUEST['force']) && $_REQUEST['force'] == '1' && yourls_url_exists($url)) {
        
        // Start transaction
        $ydb->begin_transaction();
        
        try {
            // Generate unique timestamp for log entry
            $timestamp = date('Y-m-d H:i:s');
            $ip = yourls_get_IP();
            
            // Insert the new link directly into the database
            $binds = array(
                'keyword'   => $keyword,
                'url'       => $url,
                'title'     => $title,
                'timestamp' => $timestamp,
                'ip'        => $ip,
            );
            
            $table = YOURLS_DB_TABLE_URL;
            
            // Prepare and execute the SQL query
            $insert = $ydb->fetchAffected(
                "INSERT INTO `$table` (`keyword`, `url`, `title`, `timestamp`, `ip`) VALUES (:keyword, :url, :title, :timestamp, :ip)",
                $binds
            );
            
            if ($insert !== 1) {
                $ydb->rollback();
                return false;
            }
            
            // Success, commit and return the result
            $ydb->commit();
            
            // Prepare result
            $return = array(
                'status'    => 'success',
                'code'      => '',
                'url'       => array(
                    'keyword'   => $keyword,
                    'url'       => $url,
                    'title'     => $title,
                    'date'      => $timestamp,
                    'ip'        => $ip,
                    'clicks'    => 0,
                ),
                'message'   => 'Duplicate URL forced - new short URL created',
                'title'     => $title,
                'shorturl'  => yourls_link($keyword),
            );
            
            // Return the custom result instead of letting YOURLS handle it
            return yourls_apply_filter('after_force_allow_duplicates', $return, $url, $keyword, $title);
        } catch (Exception $e) {
            // Something went wrong, rollback
            $ydb->rollback();
            
            // Log the error
            error_log('YOURLS Force Allow Duplicates Error: ' . $e->getMessage());
            
            // Return false to let YOURLS handle it normally
            return false;
        }
    }
    
    // Return default to let YOURLS handle it normally
    return $pre;
}

/**
 * Legacy handler from the original plugin, with enhancements
 */
function force_allow_existing_urls($return, $url, $keyword, $title) {
    // If the force parameter is set, use the more advanced function above
    if (isset($_REQUEST['force']) && $_REQUEST['force'] == '1') {
        // The force_add_duplicate_url function will handle this
        return $return;
    }
    
    // Otherwise, for backward compatibility, modify the error to success
    if (isset($return['code'])) {
        if ($return['code'] === 'error:url') {
            if ($url_exists = yourls_url_exists($url)) {
                $return['status']     = 'success';
                $return['code']       = '';
                $return['errorCode']  = '200';
                $return['statusCode'] = '200';
                
                // Add a note to indicate this is using fallback behavior
                $return['note'] = 'URL already exists. Use force=1 parameter to create a new short URL.';
            }
        }
    }
    
    return yourls_apply_filter('after_force_allow_existing_urls', $return, $url, $keyword, $title);
}