AJAX教程

AJAX+PHP數(shù)據(jù)庫操作

為了更清楚地說明如何使用AJAX從數(shù)據(jù)庫訪問信息，我們將動態(tài)構(gòu)建MySQL查詢并在“ajax.html”上顯示結(jié)果。但在我們繼續(xù)本教程之前，需要做好一些基礎(chǔ)工作。使用以下命令創(chuàng)建表。

注：假設(shè)您有足夠的權(quán)限執(zhí)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')
)

現(xiàn)在使用以下SQL語句將以下數(shù)據(jù)轉(zhuǎn)儲(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);

客戶端HTML文件

現(xiàn)在我們創(chuàng)建客戶端HTML文件，即ajax.html，它的代碼如下：

<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：在查詢中傳遞變量的方式是根據(jù)HTTP標(biāo)準(zhǔn)表單形式。

URL?variable1=value1;&variable2=value2;

上面的代碼將生成以下表單

在輸入后，結(jié)果將顯示在此部分中。

服務(wù)器端PHP文件

上面客戶端腳本已準(zhǔn)備就緒。現(xiàn)在需要編寫服務(wù)器端腳本，它將從數(shù)據(jù)庫中獲取age，wpm和sex并將其發(fā)送回客戶端。將以下代碼放入文件“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;
?>

現(xiàn)在嘗試在Max Age或任何其他框中輸入有效值(例如120)，然后單擊Query MySQL按鈕。

如果您已成功完成本課程，那么應(yīng)該撐握了如何使用MySQL，PHP，HTML和Javascript來編寫AJAX應(yīng)用程序。

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