ต้องการ DELETE FROM t_sec และ DELETE FROM t_regis แต่เมื่อทำงาน(ลบ)มันไม่ทำงานแต่พอลบ mysqli_query ที่ 2 ออกก็ลบได้ปัญหานี้มีวิธีแก้ยังไงครับ

<?php 
//print_r($_POST);
//exit();
session_start();// Starting Session
include('../include/connectinfo.php'); // Includes Connection Information
$data = array();
if(isset($_SESSION['ID']) && ($_SESSION['USER_STATE']==2) && ($_SESSION['USER_TYPE']>=1) ) {
	if(isset($_POST['i']))$subid= $_POST['i'];
	else $subid = '';
	
	if( ($subid=='') ){
		$data['result']=0;
		$data['text']="ไม่มีข้อมูลตอน ไม่สามารถลบได้";
		echo json_encode($data);
		exit(0);
	}
	// Establishing Connection with Server by passing server_name, user_id and password as a parameter
    $connection = mysqli_connect($__dbhost, $__dbuser, $__dbpass,$__dbname);
	if(!$connection){
        //die("Database Error: ".mysqli_error($connection));
		$data['result']=0;
		$data['text']="Database Error: ".mysqli_error($connection);
		echo json_encode($data);
		exit(0);
    }
    if (mysqli_connect_errno()) {
        //die("Connect failed: ".mysqli_connect_errno()." : ". mysqli_connect_error());
		$data['text']="Connect failed: ".mysqli_connect_errno()." : ". mysqli_connect_error();
		echo json_encode($data);
		exit(0);
    }
	mysqli_set_charset($connection,'utf8');
	// To protect MySQL injection for Security purpose
    $subid = stripslashes(trim($subid));
    $subid = mysqli_real_escape_string($connection,$subid);
    	
	$sql = "DELETE FROM `t_sec` WHERE `sec_id`='$subid';";
			
	if (!mysqli_query($connection,$sql))
	{
		//echo("การลบพบปัญหา: " . mysqli_error($connection));
		$data['result']=0;
		$data['text']="การลบพบปัญหา: " . mysqli_error($connection);
	}
	else{
		//echo ("ลบเรียบร้อย ");
		$sql = "DELETE FROM `t_regis` WHERE `sec_id`='$subid';";
		mysqli_query($connection,$sql);
		$data['result']=1;
		$data['text']="ลบเรียบร้อย ";
	}
	
	mysqli_close($connection); // Closing Connection*/
}
else { $data['result']=0;
	$data['text']="สิทธิถูกจำกัด";
}

echo json_encode($data);
?>