PHP scheduled task detects user connection status_PHP tutorial

ignore_user_abort(); // The user closes the browser and the program is still executed
set_time_limit(0); // No limit on program running time
$interval = 3; // Program loop interval seconds

$link = mysql_connect('localhost', 'username', 'paswd') ;
mysql_select_db('test');
mysql_query("SET NAMES 'utf8'");

do {
// The user closes the browser to stop start
echo str_repeat( ' ', 4069); // PHP only checks the user connection status when outputting. The default value of output_buffering for some web servers is 4096 characters. To ensure that flush() is effective, set it to 4069.
ob_flush();
flush();
// The user closes the browser and stops end

$query = "INSERT INTO `test`.`test_demo` (`title`, `content`) VALUES ('Scheduled Task' , '" . date("Y-m-d H:i:s", time()) . "')";
mysql_query($query); // Use write database verification program
sleep($interval) ;
} while (true);

// The user closes the browser to stop start
echo str_repeat(' ', 4069 ); // php only checks the user connection status when outputting. The default value of output_buffering for some web servers is 4096 characters. To ensure that flush() is effective, set it to 4069.
ob_flush();
flush() ;
// The user closes the browser to stop end