Backend DevelopmentPHP TutorialHow to use ajax in PHP to create a login page, verify whether the user name is available, and dynamically call the databaseHow to use ajax in PHP to create a login page, verify whether the user name is available, and dynamically call the database
1.Basic knowledge of ajax
ajax is a comprehensive application technology extended by combining jquery, php and other technologies. It is not new content. Ajax is also written in the <script> tag. </script>
If you use ajax, you must have a processing page. The processing page only operates the database and returns values. The pages are all processed by ajax.
2. Use ajax to create the login page denglu.php
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<script src="../jquery-1.11.2.min.js"></script>
<title>无标题文档</title>
</head>
<body>
<p>用户名：<input type="text" id="uid" /></p>
<p>密码：<input type="text" id="pwd" /></p>
<p><input type="button" value="登录" id="btn" /></p>
</body>
<script type="text/javascript">$(document).ready(function(e) {
$("#btn").click(function(){//给按钮加点击事件
//取用户名和密码
var u = $("#uid").val();//取输入的用户名
var p = $("#pwd").val();//取输入的密码
//调ajax
$.ajax({
url:"dengluchuli.php",
data:{u:u,p:p},//第二个u和p只是变量，可以随意写，dengluchuli.php里面的u和p都是第一个。
type:"POST",
dataType:"TEXT",
success: function(data){ if(data.trim()=="OK")//要加上去空格，防止内容里面有空格引起错误。 {
window.location.href="main.php";//js跳转页面，要记住。 } else
{ echo("用户名或密码错误");
}
}
});
})
});</script>
</html>The login processing page dengluchuli.php
<?php
$uid = $_POST["u"];
$pwd = $_POST["p"];
include("./DBDA.class.php");
$db = new DBDA();
$sql = "select password from login where username='{$uid}'";
$mm = $db->StrQuery($sql,0);
if($mm == $pwd && $pwd!="")
{
echo "OK";
}
else
{
echo "NO";
}3. Use ajax Verify whether the user name is available testuid.php
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<script src="../jquery-1.11.2.min.js"></script>
<title>无标题文档</title>
</head>
<body>
<input type="text" id="uid" />
<span id="ts"></span>
</body>
<script type="text/javascript">
$("#uid").blur(function(){//blur表示失去焦点时触发
//取用户名
var uid = $("#uid").val();
//调ajax
$.ajax({
url:"uidchuli.php",
data:{u:uid},
type:"POST",
dataType:"TEXT",
success: function(data){
if(data>0)
{
$("#ts").html("该应户名已存在");
$("#ts").css("color","red");
}
else
{
$("#ts").html("该应户名可用");
$("#ts").css("color","green");
}
}
});
})
</script>
</html>Process page uidchuli.php
##
<?php
$uid = $_POST["u"];
include("./DBDA.class.php");
$db = new DBDA();
$sql = "select count(*) from login where username=' {
$uid
}
'";
echo $db->StrQuery($sql,0);The effect is as shown: 
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<script src="../jquery-1.11.2.min.js"></script>
<title>无标题文档</title>
</head>
<body>
<br />
<p>
<input type="text" id="name" />
</p>
<p id="list"></p>
</body>
<script type="text/javascript">$("#name").keyup(function(){ //取名称
var n = $(this).val(); if(n!="")
{ //调ajx
$.ajax({
url:"listchuli.php",
data:{n:n},
type:"POST",
dataType:"TEXT",
success: function(data){ var sz = data.split("|");
var str = "";
for(var i=0;i<sz.length;i++)
{
str = str+"<p class='l'>"+sz[i]+"</p>";
}
$("#list").html(str);
}
});
} else
{
$("#list").html("");
}
})</script>
</html>Processing page listchuli.php<?php
$name = $_POST["n"];
include("./DBDA.class.php");
$db = new DBDA();
$sql = "select areaname from chinastates where areaname like'% {
$name
}
%'";
echo $db->StrQuery($sql,0);The effect is as shown in the figure: 
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