我應該使用什麼函數來讀取大文件的第5行？

Question

我應該用什麼php函數來計算大文件的第5行，因爲第5行是帶寬？數據的

實施例：

103.239.234.105 -- [2007-04-01 00:42:21] "GET articles/learn_PHP_basics HTTP/1.0" 200 12729 "Mozilla/4.0" 

Answer 1

打開文件到一個手柄：

$handle = fopen("someFilePath", "r"); 

然後讀取所述第一5行，並且只保存第五：

$i = 0; 
$fifthLine = null; 
while (($buffer = fgets($handle, 4096)) !== false) { 
    if $i++ >= 5) { 
     $fifthLine = $buffer; 
     break; 
    } 
} 
fclose($handle); 
if ($i < 5); // uh oh, there weren't 5 lines in the file! 
//$fifthLine should contain the 5th line in the file 

注這是流式傳輸，因此它不會加載整個文件。

Answer 2

如果你想讀每5日線，你可以使用一個SplFileObject，使生活變得更輕鬆（除fopen/fgets/fclose家庭的功能）。

$f = new SplFileObject('myreallybigfile.txt'); 

// Read ahead so that if the last line in the file is a 5th line, we echo it. 
$f->setFlags(SplFileObject::READ_AHEAD); 

// Loop over every 5th line starting at line 5 (offset 4). 
for ($f->rewind(), $f->seek(4); $f->valid(); $f->seek($f->key()+5)) { 
    echo $f->current(); 
} 

Answer 3

http://tekkie.flashbit.net/php/tail-functionality-in-php

<?php 

// full path to text file 
define("TEXT_FILE", "/home/www/default-error.log"); 
// number of lines to read from the end of file 
define("LINES_COUNT", 10); 


function read_file($file, $lines) { 
    //global $fsize; 
    $handle = fopen($file, "r"); 
    $linecounter = $lines; 
    $pos = -2; 
    $beginning = false; 
    $text = array(); 
    while ($linecounter > 0) { 
     $t = " "; 
     while ($t != "\n") { 
      if(fseek($handle, $pos, SEEK_END) == -1) { 
       $beginning = true; 
       break; 
      } 
      $t = fgetc($handle); 
      $pos --; 
     } 
     $linecounter --; 
     if ($beginning) { 
      rewind($handle); 
     } 
     $text[$lines-$linecounter-1] = fgets($handle); 
     if ($beginning) break; 
    } 
    fclose ($handle); 
    return array_reverse($text); 
} 

$fsize = round(filesize(TEXT_FILE)/1024/1024,2); 

echo "<strong>".TEXT_FILE."</strong>\n\n"; 
echo "File size is {$fsize} megabytes\n\n"; 
echo "Last ".LINES_COUNT." lines of the file:\n\n"; 

$lines = read_file(TEXT_FILE, LINES_COUNT); 
foreach ($lines as $line) { 
    echo $line; 
}