表单各项一定要加name属性，POST 和GET 取值都是通过name属性传参数获取的。不设置NAME属性获取不到值。

HTML JS PHP MYSQL 字符集 最好统一。

HTML JS PHPHTTP 请求方式必须统一。

举例：

html代码：

<formid="reg_form"method="post"action="reg_submit.php"onsubmit="returncheck_form(this)"name="reg_form"><inputtype="text"id="username_input"name="username_input"onblur="check_username()"onkeyup="check_username()"/><inputtype="text"id="email_input"name="email_input"onblur="check_email()"onkeyup="check_email()"/><inputtype="password"id="password_input"name="password_input"onblur="check_password()"onkeyup="check_password()"/><inputtype="password"id="repassword_input"name="repassword_input"onblur="check_repassword()"onkeyup="check_repassword()"/><inputtype="text"id="name_input"name="name_input"/><inputtype="submit"id="tijiao"value=""name="tijao"/><inputtype="button"id="quxiao"value=""name="quxiao"/><inputtype="hidden"id="username_check"value="0"/><inputtype="hidden"id="email_check"/value="0"></form>

PHP代码：

<?phpheader("Content-type:text/html;charset=UTF-8");error_reporting(0);$username_value=$_POST['username_input'];$email_value=$_POST['email_input'];$password_value=$_GET['password_input'];$name_value=$_POST['name_input'];include('data/conn.php');//$regdate=time();$sql="INSERTINTOt_user(f_username,f_email,f_password,f_name)VALUES('$username_value','$email_value','$password_value','$name_value')";if(mysql_query($sql,$conn)){echo$username_value;//echo$sql;打印执行时的SQL语句//echo$password_value;//打印传递的密码值exit('用户恭喜注册成功！点击此处<ahref="login.html">登录</a>');}else{echo'抱歉！添加数据失败：',mysql_error(),'<br/>';echo'点击此处<ahref="javascript:history.back(-1);">返回</a>重试';}?>