================>ALTER TABLE `phppos_app_config` ADD `cmandatory` VARCHAR( 255 ) NOT NULL 

================>SALES.php[controllers]


	$customer_id=$this->sale_lib->get_customer();
		if ($this->Appconfig->get('cmandatory') && ($customer_id==-1))
{
	echo "<script>alert('Sales can not be completed,to select customer  is mandatory');</script>";
$this->_reload();
return ;
	
}
===============>config.php [controllers]
	'cmandatory'=>$this->input->post('cmandatory')	


===============>config.php [views]

<div class="field_row clearfix">	
<?php echo form_label('Select Sales-Customer  mandatory'.':', 'print_after_sale',array('class'=>'wide')); ?>
	<div class='form_field'>
	<?php echo form_checkbox(array(
		'name'=>'cmandatory',
		'id'=>'cmandatory',
		'value'=>'cmandatory',
		'checked'=>$this->config->item('cmandatory')));?>
	</div>
</div>
 