使用PHP实现用户登录和注册的功能

登陆界面 login.php

<form action="logincheck.php" method="post">
	用户名：<input type="text" name="username" />
    <br />
    密码：<input type="password" name="password" />
    <br />
    <input type="submit" name="submit" value="登陆" />
        
    <a href="register.php">注册</a>
</form>

<?php
	if(isset($_POST["submit"]) && $_POST["submit"] == "登陆")
	{
		$user = $_POST["username"];
		$psw = $_POST["password"];
		if($user == "" || $psw == "")
		{
			echo "<script>alert("请输入用户名或密码！"); history.go(-1);</script>";
		}
		else
		{
			mysql_connect("localhost","root","sixx");
			mysql_select_db("vt");
			mysql_query("set names "gbk"");
			$sql = "select username,password from user where username = "$_POST[username]" and password = "$_POST[password]"";
			$result = mysql_query($sql);
			$num = mysql_num_rows($result);
			if($num)
			{
				$row = mysql_fetch_array($result);	//将数据以索引方式储存在数组中
				echo $row[0];
			}
			else
			{
				echo "<script>alert("用户名或密码不正确！");history.go(-1);</script>";
			}
		}
	}
	else
	{
		echo "<script>alert("提交未成功！"); history.go(-1);</script>";
	}

?>

<form action="regcheck.php" method="post">
	用户名：<input type="text" name="username"/>
    <br/>
    密　码:<input type="password" name="password"/>
    <br/>
    确认密码：<input type="password" name="confirm"/>
    <br/>
    <input type="Submit" name="Submit" value="注册"/>
</form>

<?php
	if(isset($_POST["Submit"]) && $_POST["Submit"] == "注册")
	{
		$user = $_POST["username"];
		$psw = $_POST["password"];
		$psw_confirm = $_POST["confirm"];
		if($user == "" || $psw == "" || $psw_confirm == "")
		{
			echo "<script>alert("请确认信息完整性！"); history.go(-1);</script>";
		}
		else
		{
			if($psw == $psw_confirm)
			{
				mysql_connect("localhost","root","sixx");	//连接数据库
				mysql_select_db("vt");	//选择数据库
				mysql_query("set names "gdk"");	//设定字符集
				$sql = "select username from user where username = "$_POST[username]"";	//SQL语句
				$result = mysql_query($sql);	//执行SQL语句
				$num = mysql_num_rows($result);	//统计执行结果影响的行数
				if($num)	//如果已经存在该用户
				{
					echo "<script>alert("用户名已存在"); history.go(-1);</script>";
				}
				else	//不存在当前注册用户名称
				{
					$sql_insert = "insert into user (username,password,phone,address) values("$_POST[username]","$_POST[password]","","")";
					$res_insert = mysql_query($sql_insert);
					//$num_insert = mysql_num_rows($res_insert);
					if($res_insert)
					{
						echo "<script>alert("注册成功！"); history.go(-1);</script>";
					}
					else
					{
						echo "<script>alert("系统繁忙，请稍候！"); history.go(-1);</script>";
					}
				}
			}
			else
			{
				echo "<script>alert("密码不一致！"); history.go(-1);</script>";
			}
		}
	}
	else
	{
		echo "<script>alert("提交未成功！"); history.go(-1);</script>";
	}
?>