Demonstrates how to set up a multiple-field match when a signup form is submitted or importing a CSV to Participants Database

pdb-multi-field-match-import.php

<?php
/*
 * Plugin Name: PDb Multi-Field Match Import
 * Description: Demonstrates how to set up a multiple-field match when a signup form is submitted or importing a CSV to Participants Database
 * Version: 2.0
 * 
*/
class PDb_Multifield_Match_Import {
  
  /**
   * @var array list of fields to match on import
   *
   * set this array to the fields that must match between the incoming data
   * and the database
   */
  private $match_field_list = array( 'first_name', 'last_name' );
  
  /**
   * @var int this holds the ID of the matched record or int 0 if no match
   */
  private $match_id = 0;
  
  /**
   * @var bool if true, only apply the multi-field match to CSV imports
   *
   * if false, this will also attempt to match records on a signup form submission
   * 
   * by default, this plugin only looks at CSV imports for a match
   */
  private $import_only = true;
  
  /**
   * sets up our filters
   */
  public function __construct()
  {
    add_action( 'pdb-incoming_record_match_object', array( $this, 'check_for_match' ), 10, 3 );
    add_filter( 'pdb-process_form_matched_record', array( $this, 'provide_the_matched_id' ) );
  }
  
  /**
   * checks the incoming data against the database to find a match
   *
   * @param \PDb_submission\matching\record $match object
   */
  public function check_for_match( $match )
  {
    if ( $this->skip_this_match( $match ) )
    {
      return;
    }
    
    // set the match_id property to the result of our search
    $this->match_id = $this->check_db_for_match( $this->match_data( $match->post ) );
    
    // return true if we have a match
    $match->set_match_status( $this->match_id !== false );
  }
  
  /**
   * checks to see if the incoming match should be skipped
   * 
   * @param \PDb_submission\matching\import $match object
   * @return bool true to skip matching the submission
   */
  private function skip_this_match( $match )
  {
    if ( $this->import_only && ! $match->is_csv_import() )
    {
      return true;
    }
    
    // if the posted data doesn't have the match fields present, don't attempt a match
    if ( count( array_intersect( array_keys( $match->post ), $this->match_field_list ) ) !== count( $this->match_field_list ) )
    {
      return true;
    }
    
    return false;
  }
  
  /**
   * supplies the matched id
   * 
   * @param int $match_id the matched id found by the standard method (we ignore this)
   * 
   * @return int  the matched record ID
   */
  public function provide_the_matched_id( $match_id )
  {
    return $this->match_id;
  }
  
  /**
   * queries the database with the match field data to find a match
   *
   * @global wpdb $wpdb
   * @param array $match_data the data to use in finding the match as $name => $value
   *
   * @return int|bool the record ID if there is a match, bool false if no match
   */
  private function check_db_for_match( $match_data )
  {
    $query = 'SELECT `id` FROM ' . Participants_Db::$participants_table . ' WHERE ' . $this->where_clause();
    
    global $wpdb;
    $result = $wpdb->get_col( $wpdb->prepare( $query, $match_data ) );
    
    // add debugging to make sure the query and result is as expected
    Participants_Db::debug_log(__METHOD__.' query: '.$wpdb->last_query.' result: '.print_r($result,1), 2);
    
    // make sure there is only one match, then return the found ID
    if ( count( $result ) === 1 ) {
      return current( $result );
    }
    
    // no match or more than one match
    return false;
  }
  
  /**
   * provides the where clause
   *
   * @return string where clause forthe match query
   */
  private function where_clause()
  {
    $where_clause = array();
    // make an array of all the subclauses
    foreach ( $this->match_field_list as $field ) {
      $where_clause[] = '`' . $field . '` = "%s"';
    }
    // string them all together to build the clause
    return implode( ' AND ', $where_clause);
  }
  
  /**
   * provides the match data array
   * 
   * this extracts the match field data from the posted data
   * 
   * @param array $post the posted data
   * 
   * @return array the extracted data
   */
  private function match_data( $post )
  {
    $match_data = array();
    foreach ( $this->match_field_list as $field ) {
      $match_data[] = isset( $post[$field] ) ? $post[$field] : ''; 
    }
    return $match_data;
  }
  
}

 new PDb_Multifield_Match_Import;

Aug 18, 2020 Fixed an error with the argument count.

Dear Ronald,
I need to prevent duplicate records at the sign-up form. Basically, in the sign-up form I have an ID field and I need to prevent duplicate IDs.
Can you please help to prevent duplicate records by validating one filed of the sign-up form?
Thank you in advance,