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An explanation of how PHP performs database operations and prevents page timeouts and automatically refreshes pages
An explanation of how PHP performs database operations and prevents page timeouts and automatically refreshes pages
It is very common to operate the database in PHP development. If we stay on a page for a long time without operating, there will be prompts or errors. I believe everyone has encountered it. So today we will talk about how to operate the database. Take action and prevent page timeouts!
Instructions:
When initializing or modifying the database:
1. Simply use sql statements directly Finish.
2. A little more complicated, it can be completed by executing php code (read data and then write/modify data).
When using php code (not command line), we may encounter web page timeout. There are generally three solutions:
1. Set php.ini:
max_execution_time
2. Add in the code:
set_time_limit(0); //0表示不超时
3. The page refreshes automatically and completes the entire work in batches:
The page can change with the execution process, such as dynamically telling the user how far it has been executed, instead of waiting for a single page.
Below, we mainly sort out the third method.
The page automatically refreshes:
Page refresh<==>The page jumps and stops jumping when a certain condition is met.
Page jump: Output meta tags to achieve
if ($flag) {
//跳转页面，xxx为该php文件的文件名
echo '<meta http-equiv="refresh" content="0;url=xxx.php?">';
} else {
//刷新停止
}Refresh and pass parameters at the same time to control database operations:
In the meta url, we can use Get way to pass a parameter.
This parameter can be used to change the limit of the SQL statement to implement a part of the function each time.
$page = isset($_GET['page']) ? $_GET['page'] : 0;
//用$page构造sql语句或其它功能
//数据库操作或其它功能
//设置$flag
$flag = $pdostatement->rowCount() == 0; //比如数据库影响行数
//决定 跳转刷新 或 停止
if ($flag) {
//跳转页面，xxx为该php文件的文件名
echo '<meta http-equiv="refresh" content="0;url=xxx.php?page=' . ++$page . '">';
} else {
//刷新停止
}Suppose, +1 for a certain field data, specific implementation:
I am not very familiar with SQL now.
If it is just a limit limit, it may happen that the data that has been queried is queried again and executed a second time?
Personally, it is best to add the order of the primary key by
<meta charset="UTF-8">
<?php
$page = isset($_GET['page']) ? $_GET['page'] : 0;
$step = 50; //每次刷新更新 50条数据
$limit_start = $page * 50;
$dsn = "mysql:host=localhost;dbname=db_name";
try {
$pdo = new PDO($dsn, "root", "123456");
$sql = <<<SQL
SELECT col_num, col_id
FROM table_name
ORDER by col_id
LIMIT {$limit_start},{$step}
SQL;
$pdostatement = $pdo->prepare($sql);
$pdostatement->execute();
$pdostatement->setFetchMode(PDO::FETCH_NUM);
$num = $pdostatement->rowCount();
if ($num == 0) {
echo "sql执行完毕";
} else {
echo "正在执行sql<br>";
$sql_update = "UPDATE table_name ";
while (list($col_num, $col_id) = $pdostatement->fetch(PDO::FETCH_NUM)) {
$col_name++;
$sql_update .= <<<SQL
SET col_name = "{$col_num}"
WHERE col_id = "{$col_id}" ,
SQL;
}
$sql_update = substr($sql_update, 0, -1); //去掉最后的逗号
$pdostatement_update = $pdo->prepare($sql_update);
$pdostatement_update->execute();
$num_update = $pdostatement_update->rowCount();
if ($num_update == 0) {
echo $gfc_id . "修改出错，停止更新";
} else {
echo '<meta http-equiv="refresh" content="0;url=jianshu.php?page=' . (++$page) . '">';
}
}
} catch (PDOException $e) {
echo "数据库连接失败" . $e->getMessage(); //连接失败，获取错误信息
exit;
}The above is how PHP performs database operations and prevents page timeouts and automatically refreshes the page. These methods are used in our PHP development. What is used for a long time is also very popular.
Similar articles:
How to deal with php automatically refreshing the page
php database operation and database connection tutorial
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