获取最后一行之前的最后一行值和 N 行值

Question

如何使用PHP读取并回显TEXT文件最后一行之前的N行？

file.txt 中的示例

test1
test2
test3
test4
test5
test6
test7

我想获取最后一行的值和最后一行之前的 3 行。 所以结果将是：

test4
test7

这是我目前的代码（只显示最后一行）

$line = '';
$f = fopen('\\\\192.168.183.28\\wk$\\sbin\\file.txt', 'r');
            $cursor = -1;

            fseek($f, $cursor, SEEK_END);
            $char = fgetc($f);

            while ($char === "\n" || $char === "\r") {
                fseek($f, $cursor--, SEEK_END);
                $char = fgetc($f);
            }

            while ($char !== false && $char !== "\n" && $char !== "\r")
            {
                $line = $char . $line;
                fseek($f, $cursor--, SEEK_END);
                $char = fgetc($f);
            }

            $future_sn = substr($line, 28, 36);

有什么建议吗？

Answer 1

试试

$array = explode("\n", file_get_contents('file.txt'));
// counting array and get key for prev
$prev_third = count($array)-4;
echo end($array); // test7
echo $array[$prev_third]; //test4 

Answer 2

您可以使用 fgets() 来读取文件并保留一个计数器来跟踪最后一行。您可以通过 mod(%) 计数器从最后一行获得 3 行。

$handle = fopen("input.txt", "r");
$lastRow = "";
$last3Ahead = "";
$counter = 0;
$a = "";
$b = "";
$c = "";
if ($handle) {
    while (($line = fgets($handle)) !== false) {
    if($counter == 0) $a = $line;
    if($counter == 1) $b = $line;
    if($counter == 2) $c = $line;
    $lastRow = $line ;

    if($counter >= 3) {
      $last3Ahead  = $a;
      $a = $b;
      $b = $c;
      $c = $line
    } 
    $counter++;


 } else {
// error opening the file.
 } 
  fclose($handle);
  echo $lastRow. "<br>" ;     //last row
  echo $last3Ahead  . "<br>"; //3 row before last;