PHP如何进行数据库操作以及防止页面超时和自动刷新页面讲解

max_execution_time

set_time_limit(0);  
//0表示不超时

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
}

$page = isset($_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
}

<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;
}