Question

我正在用PHP编写聊天，我想限制聊天文件中的行数：

<?php
    $filename = "chat.txt";

    file_put_contents($filename, file_get_contents($filename) . $_POST["message"] . "\r\n");

    $max_lines = 3;
    $lines = 0;

    $handle = fopen($filename, "r");
    while (!feof($handle)) {
      $line = fgets($handle);
      $lines++;
    }
    fclose($handle);

    $lines_over = $lines - $max_lines;
    if ($lines_over > 0) {
        while ($lines_over > 0) {
            file_put_contents($filename, implode("\r\n", file($filename, FILE_IGNORE_NEW_LINES)));

            $lines_over--;
        }
    }
?>

，我想在开头删除尽可能多的行，使文件只有3行。

显然这与我目前的代码无关，我不知道为什么，请帮忙吗？

Answer 1

我没有完全理解你正在尝试使用的逻辑。如果要删除文件开头的行，可以使用它。我在代码中添加了解释。

$filename = "chat.txt";
$max_lines = 3;
//Read lines into an array
$lines = file($filename);
//trim your array to max_lines
$lines = array_slice($lines, -1 * $max_lines);
//check if we have max_lines
if (count($lines) == $max_lines){
    //remove one from the beginning
    array_shift($lines);
}
//add your new line
$lines[] = trim($_POST["message"]) . "\r\n";
file_put_contents($filename, implode($lines));

参考文献：file，array_shift和array_slice

编辑：不使用array_shift

的另一种方法

$filename = "chat.txt";
$max_lines = 3;
//Read lines into an array
$lines = file($filename);
//trim your array to just one less item than max lines
$lines = array_slice($lines, -1*($max_lines-1));
//confirm newline is available in the last line
$lines[count($lines)-1] = trim($lines[count($lines)-1]) . "\r\n";
//add your new line with newline
$lines[] = trim($_POST["message"]) . "\r\n";
file_put_contents($filename, implode($lines));

Edit2：解决了尚未创建空文件和文件的问题。

$filename = "chat.txt";
$max_lines = 3;
//Read lines into an array only if file_exists
//On first run this file may not be there
if(file_exists($filename)){
    $lines = file($filename);
}
//trim your array to just one less item than max lines
//This is needed only if there are lines
if (!empty($lines)){
    $lines = array_slice($lines, -1*($max_lines-1));
    //confirm newline is available in the last line
    $lines[count($lines)-1] = trim($lines[count($lines)-1]) . "\r\n";
}
//add your new line with newline
$lines[] = trim($_POST["message"]) . "\r\n";
file_put_contents($filename, implode($lines));

注意：我没有添加用于防止浏览器刷新和多次添加相同消息的验证。这留给你实现。

PHP - 将txt文件中的行移到限制的行数

1 个答案: