About PHP - Interaction between AJAX and MySQL-PHP Tutorial-php.cn

About PHP - Interaction between AJAX and MySQL

jacklove

Release： 2023-03-25 14:36:01

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AJAX can be used to communicate interactively with the database. It is very important for PHP. This article will explain it.

AJAX database example

The following example will demonstrate how a web page reads information from the database through AJAX:

The Websites table SQL file used in this tutorial: websites.sql.

Example

Select a website: Google Taobao Rookie Tutorial Weibo Facebook

Select the corresponding option, the user information will be displayed here...

Instance explanation - MySQL database

In the above example, the database table we use is as follows:

mysql> select * from websites;+----+--------------+---------------------------+-------+---------+| id | name         | url                       | alexa | country |+----+--------------+---------------------------+-------+---------+| 1  | Google       | https://www.google.cm/    | 1     | USA     || 2  | 淘宝       | https://www.taobao.com/   | 13    | CN      || 3  | 菜鸟教程 | http://www.runoob.com/    | 4689  | CN      || 4  | 微博       | http://weibo.com/         | 20    | CN      || 5  | Facebook     | https://www.facebook.com/ | 3     | USA     |+----+--------------+---------------------------+-------+---------+5 rows in set (0.01 sec)

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Explanation of examples - HTML page

When the user selects a user in the above drop-down list, the function named "showSite()" will be executed. This function is triggered by the "onchange" event:

test.html File code:

<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>菜鸟教程(runoob.com)</title> <script>
function showSite(str){
    if (str=="")
    {
        document.getElementById("txtHint").innerHTML="";        return;    } 
    if (window.XMLHttpRequest)
    {
        // IE7+, Firefox, Chrome, Opera, Safari 浏览器执行代码
        xmlhttp=new XMLHttpRequest();    }
    else
    {
        // IE6, IE5 浏览器执行代码
        xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");    }
    xmlhttp.onreadystatechange=function()
    {
        if (xmlhttp.readyState==4 && xmlhttp.status==200)
        {
            document.getElementById("txtHint").innerHTML=xmlhttp.responseText;        }
    }
    xmlhttp.open("GET","getsite_mysql.php?q="+str,true);    xmlhttp.send();}
</script></head><body>
 <form><select name="users" onchange="showSite(this.value)"><option value="">选择一个网站:</option><option value="1">Google</option><option value="2">淘宝</option><option value="3">菜鸟教程</option><option value="4">微博</option><option value="5">Facebook</option></select></form><br><div id="txtHint"><b>网站信息显示在这里……</b></div>
 </body></html>

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showSite() function will perform the following steps:

Check whether a website is selected

Create an XMLHttpRequest object

Create a function that is executed when the server response is ready

Send a request to a file on the server

Please note the parameters added to the end of the URL (q) (Contains the contents of the drop-down list)

PHP file

The server page called through JavaScript in the above paragraph is a PHP file named "getsite_mysql.php". The source code in

"getsite_mysql.php" will run a query against the MySQL database and return the results in an HTML table:

getsite_mysql.php File code:

<?php$q = isset($_GET["q"]) ? intval($_GET["q"]) : &#39;&#39;; 
if(empty($q)) {
    echo &#39;请选择一个网站&#39;;    exit;}
 $con = mysqli_connect(&#39;localhost&#39;,&#39;root&#39;,&#39;123456&#39;);if (!$con){
    die(&#39;Could not connect: &#39; . mysqli_error($con));}// 选择数据库mysqli_select_db($con,"test");// 设置编码，防止中文乱码mysqli_set_charset($con, "utf8"); 
$sql="SELECT * FROM Websites WHERE id = &#39;".$q."&#39;"; 
$result = mysqli_query($con,$sql); 
echo "<table border=&#39;1&#39;>
<tr>
<th>ID</th>
<th>网站名</th>
<th>网站 URL</th>
<th>Alexa 排名</th>
<th>国家</th>
</tr>"; 
while($row = mysqli_fetch_array($result)){
    echo "<tr>";    echo "<td>" . $row[&#39;id&#39;] . "</td>";    echo "<td>" . $row[&#39;name&#39;] . "</td>";    echo "<td>" . $row[&#39;url&#39;] . "</td>";    echo "<td>" . $row[&#39;alexa&#39;] . "</td>";    echo "<td>" . $row[&#39;country&#39;] . "</td>";    echo "</tr>";}echo "</table>"; 
mysqli_close($con);?>

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Explanation: When a query is sent from JavaScript to a PHP file, what happens is:

PHP opens a connection to the MySQL database

Finds the selected user

Creates the HTML table, Fill in the data and send back the "txtHint" placeholder

This article provides a detailed explanation of the interaction between PHP - AJAX and MySQL. For more learning materials, please pay attention to the php Chinese website.

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