Let's talk about how to perform scheduled query data refresh in PHP

When developing web applications, it is sometimes necessary to regularly query data in the database and update their display status on the page. PHP, as a popular back-end language, provides some methods to achieve this function. This article will introduce how to use PHP to refresh scheduled query data.

1. Use PHP to implement timers

PHP provides two functions to implement timer functions: sleep() and usleep(). These two functions can make the script hang for a period of time before executing the subsequent code. The difference between sleep() and usleep() is that the unit of sleep() is seconds and the unit of usleep() is microseconds.

For example, the following code will query the data in the database every 10 seconds:

while (true) {
    // 查询数据库
    // 更新页面显示状态
    
    sleep(10);
}

The above code uses a while loop to perform query and update operations, and then calls the sleep() function Hang for 10 seconds. You can use Ctrl C or other means to force stop the loop.

2. Use PHP to query the database regularly

In order to achieve real-time refresh of data on the page, you need to query the data in the database regularly. The key to implementing this functionality using PHP is to use a timer and perform query operations within a specified time interval.

The following is a sample code that uses PHP to query data regularly:

<?php // 连接数据库
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";
$conn = new mysqli($servername, $username, $password, $dbname);

// 查询数据
function getData() {
    global $conn;

    $sql = "SELECT * FROM myTable";
    $result = $conn->query($sql);

    $data = array();
    if ($result->num_rows > 0) {
        while($row = $result->fetch_assoc()) {
            $data[] = $row;
        }
    }

    return $data;
}

// 更新页面显示状态
function refreshPage($data) {
    echo "

";     foreach ($data as $item) {         echo "
• " . $item["name"] . "
";     }     echo "

"; } // 定时查询数据并更新页面显示状态 while (true) {     // 查询数据并更新页面     $data = getData();     refreshPage($data);     // 挂起2秒钟     usleep(2000000); } ?>

In the above sample code, a while loop is used, and the usleep() function is called at the end of each loop to hang for 2 seconds. bell. In the loop, call the getData() function to query the data in the database, and then use the refreshPage() function to update the display status on the page.

Summary

Using PHP for scheduled query data refresh allows web applications to respond to user data changes in real time. PHP provides sleep() and usleep() functions to help us implement the timer function. In order to update the data of the page in real time, it is necessary to query the data and update the display status of the page within a specified time interval.

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