let’s create WordPress plugin the easy way:

01. Create plug-in template as follows:

• Browse to http://wppb.me/ and generate plugin, this is Wordpress boilerplate generator  and generates OOP plugin.
• Download the generated plug-in.
• Install it.
• In general here is a link to wordpress developer resources.

02. plugin code

• Search plugin directory for string “public static function activate()“.
• activation: in the activation phase we will install and create the wp_db table
• find the “public static function activate()” and add code to create the db table

• public static function activate() {
      /**Create an instance of the database class**/
      if (!isset($wpdb)) $wpdb = $GLOBALS['wpdb'];
      /**Set the custom table **/$table_name = $wpdb->prefix . "crud_links";
      $demo_browser_db_version = '1.0';
      /**Execute the sql statement to create or update the custom table**/
  
      if ( $wpdb->get_var("show tables like '$table_name'" ) != $table_name ) {
          $sql = "CREATE TABLE " . $table_name . " (
          ID int(11) NOT NULL AUTO_INCREMENT,
          Name varchar(255) DEFAULT NULL,
          Link varchar(255) DEFAULT NULL,
          LinkOrder int(11) NOT NULL,
          Description varchar(2255) DEFAULT NULL,
          OpenWindow tinyint(1) NOT NULL,
          PRIMARY KEY (ID)
          ) ENGINE=MyISAM DEFAULT CHARSET=utf8 AUTO_INCREMENT=5 ;";
          require_once(ABSPATH . 'wp-admin/includes/upgrade.php');
          dbDelta($sql);
          add_option( "my_plugin_db_version", '1.0' );
      }
  
  }

• uninstall.php – when we remove the plugin this code will run

• if ( ! defined( 'WP_UNINSTALL_PLUGIN' ) ) {
      exit;global $wpdb;
      $table_name = $wpdb->prefix . "crud_links";
      $sql = "DROP TABLE IF EXISTS $table_name;";
      $wpdb->query($sql);
      delete_option("my_plugin_db_version");
  }
  

• wp hooks – admin menu
• Search plug-in directory for string private function define_admin_hooks().
• Add to this function the following line of code:

$this->loader->add_action( ‘admin_menu’, $plugin_admin, ‘admin_menu’ );

• this will call the function in admin folder
• Add the following code to php file under admin directory, not the index.php file, this will create admin page:

  public function admin_menu() {
      add_menu_page("CRUD Operation", "Links Crud", 1, "admin_linkesmenu", array($this,"admin_links_display"));
  }

  function admin_links_display()
  {
      include('partials/general-links-admin-display.php');
  }
  

• Php file under Directory Admin\Partials, general-links-admin-display.php, Insert all html + php code and CRUD action you need for back-end.

 <? php

/**
 * Provide a dashboard view for the plugin
 *
 * This file is used to markup the public-facing aspects of the plugin.
 *
 * @link: http://www.flash-jet.com
 * @since 1.0.0
 *
 * @package General_Links
 * @subpackage General_Links/admin/partials
 */
 ?>

 <!-- This file should primarily consist of HTML with a little bit of PHP. -->

<?php
global $wpdb; 
/**Set the custom table **/
$table_name = $wpdb->prefix . "crud";


$CN =mysql_connect(DB_HOST,DB_USER,DB_PASSWORD) or die("Sorry Connection Problem");
$DB =mysql_select_db(DB_NAME,$CN) or die("Sorry Not Connect to Your Database");


if(isset($_POST['add']))
{
 $name=$_POST['name'];
 $link=$_POST['link'];
 $order=$_POST['order'];
 $description=$_POST['description'];
 $openwindow=$_POST['openwindow'];
 
 $sql="INSERT INTO wp_crud_links (`Name`, `Link`, `LinkOrder`, `Description`, `OpenWindow`) VALUES ('".$name."','".$link."','".$order."','".$description."','".$openwindow."')";
 $res=mysql_query($sql);
 if($res)
 {
 echo "<script>document.location='admin.php?page=admin_linkesmenu&msg=1'</script>";
 }
 else
 {
 echo "Error !";
 }
 
}

if(isset($_POST['Update']))
{
 $uid=$_GET['id'];

 $name=$_POST['name'];
 $link=$_POST['link'];
 $order=$_POST['order'];
 $description=$_POST['description'];
 $openwindow=$_POST['openwindow'];

 $sql="update wp_crud_links set Name='".$name."' , Address='".address."' , Mobile='".$mobile."' , Fileupload='".$image_name."' where ID='".$uid."'";
 $reg=mysql_query($sql);
 if($reg)
 {
 echo"<script>document.location='admin.php?page=admin_linkesmenu&msg=2'</script>";
 }
 else
 {
 echo"Error !";
 }
}
 
if($_GET['action'] == 'delete')
{

 $did=$_GET['id'];
 
 $sql1="delete from wp_crud_links where ID='".$did."'";
 $res1=mysql_query($sql1);
 if($res1)
 {
 echo"<script>document.location='admin.php?page=admin_linkesmenu&msg=3'</script>";
 }
 else
 {
 echo "Error !";
 } 
}
?>


<?php 
if(isset($_GET['action']) && ($_GET['action'] == 'edit'))
{
 $urid=$_GET['id'];
 $sql="select * from wp_crud_links where ID='".$urid."'";
 $reg=mysql_query($sql);
 $res=mysql_fetch_array($reg);
 $uname= $res['Name'];
 $ulink= $res['Link'];
 $uorder= $res['LinkOrder'];
 $udescription= $res['Description'];
 $uopenwindow= $res['OpenWindow'];
 
 ?>
 
<form name="add" action="" method="post">
<table cellpadding="5" cellspacing="5">
 <tr>
 <td>Name :</td>
 <td><input type="text" name="name" value="<?php echo $uname; ?>" /></td></tr>
 </tr>
 <tr>
 <td>Link :</td>
 <td><input type="text" name="link" value="<?php echo $ulink; ?>" /></td></tr>
 </tr>
 <tr>
 <td>Order :</td>
 <td><input type="text" name="order" value="<?php echo $uorder; ?>" /></td></tr>
 </tr>
 <tr>
 <td>Description :</td>
 <td><textarea name="description" rows="3" cols="50"> <?php echo $udescription; ?></textarea></td></tr>
 </tr>
 <tr>
 <td>Open in new window :</td>
 <td><input type="checkbox" name="openwindow" value="<?php echo $uopenwindow; ?>" <?php echo ($uopenwindow == 1 ? 'checked' : '') ?> /></td></tr>
 </tr>
 
 <td><input type="submit" name="Update" value="update" align="middle"/>
 <a href="admin.php?page=admin_linkesmenu" style="text-decoration:none;"><input type="button" name="cancel" value="Cancel" id="html-upload" align="middle"></a>
 </td>
 </tr>

</table>
</form>

<?php }elseif(isset($_GET['action']) && ($_GET['action'] == 'add'))
{ ?>
<hr>
<form name="add" action="" method="post">
 <table cellpadding="5" cellspacing="5">
 <tr>
 <td>Name :</td>
 <td><input type="text" name="name" /></td></tr>
 </tr>
 <tr>
 <td>Link :</td>
 <td><input type="text" name="link" /></td></tr>
 </tr>
 <tr>
 <td>Order :</td>
 <td><input type="text" name="order" /></td></tr>
 </tr>
 <tr>
 <td>Description :</td>
 <td><textarea name="description" rows="3" cols="50"></textarea></td></tr>
 </tr>
 <tr>
 <td>Open in new window :</td>
 <td><input type="checkbox" name="openwindow" value="1" /></td></tr>
 </tr>
 <tr>
 <td>
 <input type="submit" name="add" value="Add" align="middle"/>
 <a href="admin.php?page=admin_linkesmenu" style="text-decoration:none;"><input type="button" name="cancel" value="Cancel" id="html-upload" align="middle"></a>
 </td>
 </tr>
 
 </table>
</form>
 
<?php } else { ?>
<?php if($_GET['msg'] == 1) { ?>
<h2><center> Record Sucessfull Added</center></h2>
<?php } ?>

<?php if($_GET['msg'] == 2) { ?>
<h2><center> Record Sucessfull Updated</center></h2>
<?php } ?>

<?php if ($_GET['mag'] == 3){?>
<h2><center> Record Sucessfull Deleted</center></h2>
<?php } ?>

<div class="wrap" style="float:none;">
 <h2>Simple CRUD Operation
 <a class="add-new-h2" href="admin.php?page=admin_linkesmenu&action=add">Add New</a></h2>
</div>

<table cellspacing="0" class="wp-list-table widefat fixed pages">
 <thead>
 <tr>
 <th style="width:30px;" class="" id="" scope="col"><span>No</span></th>
 <th style="width:100px;" class="" id="" scope="col"><span>Name</span></th>
 <th style="width:100px;" class="" id="" scope="col"><span>Link</span></th>
 <th style="width:100px;" class="" id="" scope="col"><span>Order</span></th>
 <th style="width:200px;" class="" id="" scope="col"><span>Description</span></th>
 <th style="width:200px;" class="" id="" scope="col"><span>OpenWindow</span></th>
 <th style="width:200px;" class="" id="" scope="col"><span></span></th>
 </tr>
 </thead>
 <tbody id="the-list">
<?php
 $i = 1;
 $sqlg = "SELECT * FROM wp_crud_links ";
 //$resg = $wpdb->get_results($sqlg);
 //foreach ( $resg as $rowg ) 
 $resg = mysql_query($sqlg);
 
 if($resg === FALSE) { 
 die(mysql_error());
 }

 
 while($rowg = mysql_fetch_array($resg))
 { 
 $FileUpload=$rowg['FileUpload'];
 $rid=$rowg['ID'];
 
 echo '<tr valign="top">';
 echo '<td>'.$i.'</td>';
 echo '<td>'.$rowg['Name'].'</td>';
 echo '<td>'.$rowg['Link'].'</td>'; 
 echo '<td>'.$rowg['LinkOrder'].'</td>';
 echo '<td>'.$rowg['Description'].'</td>';
 echo '<td><input type="checkbox" '.($rowg['OpenWindow'] == 1?'checked':'').'/></td>';
 echo '<td><a href="admin.php?page=admin_linkesmenu&action=edit&id='.$rid.'" >Edit</a>&nbsp;||&nbsp;<a href="admin.php?page=admin_linkesmenu&action=delete&id='.$rid.'" onclick="javascript:return confirm(\'Are You Sure?\')">Delete</a></td>';
 echo '</tr>';
 $i++;
 } 
?>
 </tbody>
</table>
<?php } ?>

• let’s create the front  end to display the data from the DB
• public php in wp is done via shortcodes
• private function define_public_hooks() add new line

• $this->loader->add_action( 'init', $plugin_public, 'register_shortcodes' );

• this will call register_shortcodes function in the public folder of the plugin

• public function register_shortcodes() {
      add_shortcode( 'crud_links_operation', array( $this, 'shortcode_crud_links_operation' ) );
  }
  

• this will call shortcode_crud_links_operation that will generate html to display in the shortcode
• after we create the shortcode we can insert it to a post or or page
• [crud_links_operation][/crud_links_operation] and go to wp post and she the html you inserted in the short code.