Page Comparison

private function getPrimaryKey()
{
	$primaryKey = '';
	$ds = $this->data_source;
	$fields = $ds['fields'];
	
	foreach($fields as $field)
	{
		if(array_key_exists("primaryKey", $field))
		{
			$primaryKey = $field['name'];
			return $primaryKey;
		}                       
	}
}

private function add($request)
{            
	$ds = $this->data_source;
	// get the table name from data source
	$tbl_name = $ds['ID'];
	$new_data = $request->data;
	$insert_values = array();
	// make the query            
	$columns = '';
	$values = '';
	foreach($new_data as $key => $value)
	{            
	   $columns .=  $key.',';
	   $values .=  "?,";   
	   array_push($insert_values, $value);             
	   
	}         
	// remove the last comma
	$columns = substr($columns, 0, strlen($columns) - 1);
	$values = substr($values, 0, strlen($values) - 1);
	// result insert query
	$insert_query = 'INSERT INTO '.$tbl_name.' ('.$columns.') VALUES ('.$values.')';
	
	// Run the insert query
	R::exec($insert_query, $insert_values);
	//DSResponse
	$response = new DSResponse();      
	$response->setData($new_data);            
	$response->setStatus(0);  
	return $response;
}
private function update($request)
{
	$old_data = $request->oldValues;
	$update_data = $request->data;
	$ds = $this->data_source;
	
	// update all fields which have changed. they are defined in the data property
	if ( count($request->getDataKeys()) != 0 )
	{
		 foreach($request->data as $key => $value)
		 {
			$old_data[$key] = $value;
		 }
	}     
	// get Primary key
	$primary_key = $this->getPrimaryKey();
	// get the id  by primary key
	$values = array();
	
	
	// get the table name from data source
	$tbl_name = $ds['ID'];            
	$set_value = '';
	// make the update query
	foreach($old_data as $key => $value)
	{          
		if($key != $primary_key)  
		{
			$set_value .= "$key = ?,"; 
			array_push($values, $value);                  
		}   
	}
	array_push($values, $old_data[$primary_key]);
	
	// remove the last comma
	$set_value = substr($set_value, 0, strlen($set_value) - 1);
	// result insert query
	$update_query = 'UPDATE '.$tbl_name.' SET '.$set_value.' WHERE '.$primary_key.'= ?';
	R::exec($update_query, $values);
	
	// build the criteria
	//DSResponse
	$response = new DSResponse();      
	$response->setData($old_data);            
	$response->setStatus(0);  
	return $response;
}
private function remove($request)
{
	$ds = $this->data_source;            
	// get the table name from data source
	$tbl_name = $ds['ID'];            
	$new_data = $request->data;
	// get Primary key
	$primary_key = $this->getPrimaryKey();
	// get the id  by primary key
	$value = $new_data[$primary_key];
	// make the delete query
	$delete_query = "DELETE FROM $tbl_name WHERE $primary_key = ?";
	// Run the insert query
	R::exec($delete_query, array($value));
										 
	//DSResponse
	$response = new DSResponse();      
	$response->setData($new_data);            
	$response->setStatus(0);  
	return $response;
}