AJAX教程
为了更清楚地说明如何使用AJAX从数据库访问信息，我们将动态构建MySQL查询并在“ajax.html”上显示结果。但在我们继续本教程之前，需要做好一些基础工作。使用以下命令创建表。
注：假设您有足够的权限执行以下MySQL操作。
CREATE TABLE 'ajax_users' (
'name' varchar(50) NOT NULL,
'age' int(11) NOT NULL,
'sex' varchar(1) NOT NULL,
'wpm' int(11) NOT NULL,
PRIMARY KEY ('name')
)
现在使用以下SQL语句将以下数据转储(插入)表中：
INSERT INTO 'ajax_users' VALUES ('Jerry', 120, 'm', 20);
INSERT INTO 'ajax_users' VALUES ('Regis', 75, 'm', 44);
INSERT INTO 'ajax_users' VALUES ('Frank', 45, 'm', 87);
INSERT INTO 'ajax_users' VALUES ('Jill', 22, 'f', 72);
INSERT INTO 'ajax_users' VALUES ('Tracy', 27, 'f', 0);
INSERT INTO 'ajax_users' VALUES ('Julie', 35, 'f', 90);
客户端HTML文件
现在我们创建客户端HTML文件，即ajax.html，它的代码如下：
<html>
<body>
<script language = "javascript" type = "text/javascript">
<!--
//Browser Support Code
function ajaxFunction() {
var ajaxRequest; // The variable that makes Ajax possible!
try {
// Opera 8.0+, Firefox, Safari
ajaxRequest = new XMLHttpRequest();
} catch (e) {
// Internet Explorer Browsers
try {
ajaxRequest = new ActiveXObject("Msxml2.XMLHTTP");
} catch (e) {
try {
ajaxRequest = new ActiveXObject("Microsoft.XMLHTTP");
} catch (e) {
// Something went wrong
alert("Your browser broke!");
return false;
}
}
}
// Create a function that will receive data
// sent from the server and will update
// div section in the same page.
ajaxRequest.onreadystatechange = function() {
if(ajaxRequest.readyState == 4) {
var ajaxDisplay = document.getElementById('ajaxDiv');
ajaxDisplay.innerHTML = ajaxRequest.responseText;
}
}
// Now get the value from user and pass it to
// server script.
var age = document.getElementById('age').value;
var wpm = document.getElementById('wpm').value;
var sex = document.getElementById('sex').value;
var queryString = "?age = " + age ;
queryString += "&wpm = " + wpm + "&sex=" + sex;
ajaxRequest.open("GET", "ajax-example.php" + queryString, true);
ajaxRequest.send(null);
}
//-->
</script>
<form name = 'myForm'>
Max Age: <input type = 'text' id = 'age' /> <br />
Max WPM: <input type = 'text' id = 'wpm' /> <br />
Sex:
<select id = 'sex'>
<option value = "m">m</option>
<option value = "f">f</option>
</select>
<input type = 'button' onclick = 'ajaxFunction()' value = 'Query MySQL'/>
</form>
<div id = 'ajaxDiv'>Your result will display here</div>
</body>
</html>
注：在查询中传递变量的方式是根据HTTP标准表单形式。
URL?variable1=value1;&variable2=value2;
上面的代码将生成以下表单
在输入后，结果将显示在此部分中。
上面客户端脚本已准备就绪。现在需要编写服务器端脚本，它将从数据库中获取age，wpm和sex并将其发送回客户端。将以下代码放入文件“ajax-example.php”。
<?php
$dbhost = "localhost";
$dbuser = "dbusername";
$dbpass = "dbpassword";
$dbname = "dbname";
//Connect to MySQL Server
mysql_connect($dbhost, $dbuser, $dbpass);
//Select Database
mysql_select_db($dbname) or die(mysql_error());
// Retrieve data from Query String
$age = $_GET['age'];
$sex = $_GET['sex'];
$wpm = $_GET['wpm'];
// Escape User Input to help prevent SQL Injection
$age = mysql_real_escape_string($age);
$sex = mysql_real_escape_string($sex);
$wpm = mysql_real_escape_string($wpm);
//build query
$query = "SELECT * FROM ajax_example WHERE sex = '$sex'";
if(is_numeric($age))
$query .= " AND age <= $age";
if(is_numeric($wpm))
$query .= " AND wpm <= $wpm";
//Execute query
$qry_result = mysql_query($query) or die(mysql_error());
//Build Result String
$display_string = "<table>";
$display_string .= "<tr>";
$display_string .= "<th>Name</th>";
$display_string .= "<th>Age</th>";
$display_string .= "<th>Sex</th>";
$display_string .= "<th>WPM</th>";
$display_string .= "</tr>";
// Insert a new row in the table for each person returned
while($row = mysql_fetch_array($qry_result)) {
$display_string .= "<tr>";
$display_string .= "<td>$row[name]</td>";
$display_string .= "<td>$row[age]</td>";
$display_string .= "<td>$row[sex]</td>";
$display_string .= "<td>$row[wpm]</td>";
$display_string .= "</tr>";
}
echo "Query: " . $query . "<br />";
$display_string .= "</table>";
echo $display_string;
?>
现在尝试在Max Age或任何其他框中输入有效值(例如120)，然后单击Query MySQL按钮。
如果您已成功完成本课程，那么应该撑握了如何使用MySQL，PHP，HTML和Javascript来编写AJAX应用程序。
