为什么php中使用mysqli_query()插入不了数据

<?php
require_once("get_or_close_connection.php");
//echo require_once("get_or_close_connection.php");
require_once("is_Exist_User.php");
function addUser($name, $pass, $head, $gender)
{
    if (is_Exist_Users($name)) {
        echo '<form action="index.html" method="get" name="myForm"></form>
          <script type="text/javascript"> document.forms["myForm"].submit(); </script>';
        exit("用户已存在!请重新注册");
    }
    $format = "%Y%m%d%H:%M:%S";//设置日期格式
    $regTime = strftime($format);
    $insertSQL = "insert into tbl_user values(null,'$name','$pass','$head','$regTime','$gender')";
    $database = "cxbbs";
    $get_connect = getConnection($database);
    echo mysqli_errno($get_connect);
    $rs=mysqli_query($get_connect, $insertSQL)or die("插入不成功");
    return $rs;//返回执行结果
}
?>

数据库连接正常,用post方法获取网页的信息但是,利用变量去动态插入数值 .就是插入不成功

<?php
require_once("get_or_close_connection.php");
//echo require_once("get_or_close_connection.php");
require_once("is_Exist_User.php");
function addUser($name, $pass, $head, $gender)
{
//    if (is_Exist_Users($name)) {
//        echo '<form action="index.html" method="get" name="myForm"></form>
//          <script type="text/javascript"> document.forms["myForm"].submit(); </script>';
//        exit("用户已存在!请重新注册");
//    }
    $format = "%Y%m%d%H:%M:%S";//设置日期格式
    $regTime = strftime($format);
    $insertSQL = "insert into tbl_user (uName,uPass,head,regTime,gender)values('$name','$pass','$head','$regTime','$gender')";
    $database = "cxbbs";
    $get_connect = getConnection($database);
    echo mysqli_errno($get_connect);
    $rs=mysqli_query($get_connect, $insertSQL)or die("插入不成功");
    return $rs;//返回执行结果
}
?>

    echo mysqli_errno($get_connect);

这一行报什么错