WPDB sample

custom-model-base.php

<?php
namespace SolusiPress\Model;

class Base {
    
    public $db = null;
    public $table = null;
    
    protected $sqlOrder = '';
    protected $sqlWhere = '';
    protected $filtered = array();
    protected $data_filtered = false;
    
    
    public function __construct() {
        global $wpdb;
        $this->db = $wpdb;
    }
    
    public function get_row( $post_id ) {
        $sql = $this->db->prepare( "select * from {$this->table} where post_id=%d", $post_id );
        $row = $this->db->get_row( $sql );
        return $row;
    }

    public function get_by( $field, $value, $format='%d' ) {
        $sql = $this->db->prepare( "select * from {$this->table} where {$field}={$format} and date_trashed IS NULL", $value );
        $row = $this->db->get_row( $sql );
        return $row;
    }
    
    public function get_all_by( $field, $value, $format='%d' ) {
        $sql = $this->db->prepare( "select * from {$this->table} where {$field}={$format} and date_trashed IS NULL", $value );
        $rows = $this->db->get_results( $sql );
        return $rows;
    }

    public function trash( $post_id ) {
        $check = $this->get_row( $post_id );
        if( $check ) {
            $data = array( 'date_trashed' => current_time( 'mysql' ) );
            $this->db->update( $this->table, $data, array( 'id' => $check->id ), array( '%s' ), array( '%d' ) );
        }
    }
    
    public function untrash( $post_id ) {
        $check = $this->get_row( $post_id );
        if( $check ) {
            $data = array( 'date_trashed' => null );
            $this->db->update( $this->table, $data, array( 'id' => $check->id ), array( '%s' ), array( '%d' ) );
        }
    }
        
}

custom-table-process.php

<?php
namespace SolusiPress\Model;
use SolusiPress\Model\Base as BaseModel;

class Employee extends BaseModel {
    
    private static $_instance = null;
    private $post_id = null;
    
    private function __construct() {
        parent::__construct();
        $this->table = $this->db->prefix . 'app_employees';
    }  

    private function __clone() { }

    public static function getInstance() {
        if( !is_object(self::$_instance) )
            self::$_instance = new self();        
        return self::$_instance;
    }
    
    private function get_meta( $key ) {
        $value = get_post_meta( $this->post_id, $key, true );

        if( !$value ) $value = null;     
        
        if( $key == 'empfunction_id' ) {
	       $sql = $this->db->prepare( "select * from " . $this->db->prefix.'app_empfunctions' . " where post_id=%d", $value );
	       $row = $this->db->get_row( $sql );
	       if( $row ) {
		       $value = $row->id;
	       } else {
		       $value = null;
	       }
        }
           
        return $value;
    }
    
    public function insertOrUpdate( $post_id ) {
        
        $this->post_id = $post_id;
        $check = $this->db->get_row( $this->db->prepare( "select * from {$this->table} where post_id=%d", $post_id ) );
        
        $data = [
	        'post_id' => $post_id,
	        'emp_number' => $this->get_meta( 'emp_number' ),
	        'full_name' => $this->get_meta( 'full_name' ),
	        'gender' => $this->get_meta( 'gender' ),
	        'birth_date' => $this->get_meta( 'birth_date' ),
	        'email' => $this->get_meta( 'email' ),
	        'mobile' => $this->get_meta( 'mobile' ),
	        'join_date' => $this->get_meta( 'join_date' ),
	        'empfunction_id' => $this->get_meta( 'empfunction_id' ),
	        'empfunction_date' => $this->get_meta( 'empfunction_date' ),
        ];
        
        $formats = [ '%d', '%s', '%s', '%s', '%s', '%s', '%s', '%s', '%d', '%s' ];
        
        if( $check ) {
            $this->db->update( $this->table, $data, array( 'id' => $check->id ), $formats, array( '%d' ) );
        } else {
            $this->db->insert( $this->table, $data, $formats );
        }        
        
        wp_update_post( array(
	        'ID' => $post_id,
	        'post_title' => $data['full_name']
        ) );
        
    }    
    
}