在PHP中删除行？ 这可能吗？

Question

I have been struggling to create a Simple ( really simple ) chat system for my website as my knowledge on Javascripting/AJAX are Limited after gather resources and help from many kind people I was able to create my simple chat system but left with one problem.

The messages are posted to a file called "msg.html" in this format : <p><span id="name">$name</span><span id="Msg">$message</span></p> And then using PHP and AJAX I will retrieve the messages instantly from the file using the file(); function and a foreach(){} loop withing PHP here is the code :

    <?php 
$file = 'msg.html';
$data = file($file);
$max_lines = 20;
if(count($data) > $max_lines){
    // here i want the data to be deleted from oldest until i only have 20 messages left.
}
foreach($data as $line_num => $line){
echo $line_num . " . " . $line; 
}
?>

My Question is how can i delete the oldest messages so that i am only left with the latest 20 Messages ?

Answer 1

How does something like this seem to you:

$file = 'msg.html';
$data = file($file);
$max_lines = 20;
foreach($data as $line_num => $line)
{
    if ($line_num < $max_lines)
    {
        echo $line_num . " . " . $line; 
    }
    else
    {
        unset($data[$line_num]);
    }
}
file_put_contents('msg.html', $data);
?>

http://www.php.net/manual/en/function.file-put-contents.php for more info :)