Performs some simple compatibility fixes for running WordPress using SQLite

xnau-sqlite-fix.php

<?php

/**
 * Plugin Name: Participants Database SQLite Fix
 * Description: Fixes certain syntax issues with plugin db queries
 * Author: Roland Barker, xnau webdesign
 * Version: 1.1
 * Author URI: https://xnau.com
 * License: GPL3
 */
class xnau_sqlite_query_fix {
  
  /**
   * @var array of database table names to target
   * 
   * these can be partial names
   */
  private $db_tables = ['wp_participants_database'];
  
  /**
   * @var array of keywords to check
   */
  private $keywords = ['default','order','group'];
  
  /**
   * @var string the regex pattern used to escape keywords
   */
  private $escape_pattern;

  /**
   * sets up the filter
   */
  public function __construct()
  {
    add_filter( 'query', [$this, 'fix_queries'] );
    
    $this->set_escape_pattern();
  }

  /**
   * fixes syntax issues
   * 
   * @param string $query
   */
  public function fix_queries( $query )
  {
    if ( $this->is_target_query( $query ) )
    {
      $query = $this->fix_quotes($query);
      
      $query = $this->escape_sqlite_keywords($query);

      // error_log(__METHOD__.' query: '. $query );
    }
    
    return $query;
  }
  
  /**
   * tells if the query target one of our tables
   * 
   * @param string $query
   * @return bool
   */
  private function is_target_query( $query )
  {
    foreach ( $this->db_tables as $table )
    {
      if ( strpos( $query, $table ) !== false )
      {
        return true;
      }
    }
    
    return false;
  }

  /**
   * replaces double quotes with single quotes
   * 
   * @param string $query
   * @return string
   */
  private function fix_quotes( $query )
  {
    $query = preg_replace( '/"/', "'", $query );
    
    return $query;
  }
  
  /**
   * fixes unescaped keywords
   * 
   * @param string $query
   * @return string
   */
  private function escape_sqlite_keywords( $query )
  {
    $query = preg_replace( $this->escape_pattern, '.`$1`', $query );
    
    return $query;
  }
  
  /**
   * sets up the escape pattern
   */
  private function set_escape_pattern()
  {
    $this->escape_pattern = '/(?:\.)(' . implode( '|', $this->keywords ) . ')/';
  }
    
    
}

new xnau_sqlite_query_fix();

This plugin is best installed as an MU-Plugin so that it can be first in line to apply its compatibility fixes.