How to implement reading very large files in php_PHP tutorial-PHP Tutorial-php.cn

How to implement reading very large files in php_PHP tutorial

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Release： 2016-07-13 10:22:09

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php implements the method of reading very large files,

Normally speaking, when PHP reads large files, the method we use is to read them line by line, instead of writing all the files into the memory at once. This will cause the PHP program to get stuck. Here are the instructions Let me introduce you to such an example.

Read the last few lines of data from a large file:

<&#63;php
/**
 * 取文件最后$n行
 * 
 * @param string $filename 文件路径
 * @param int $n 最后几行
 * @return mixed false表示有错误，成功则返回字符串
 */
function FileLastLines($filename, $n){
   if(!$fp = fopen($filename, 'r')){
    echo "打开文件失败，请检查文件路径是否正确，路径和文件名不要包含中文";
    return false;
    }
  $pos = -2;
  $eof = "";
  $str = "";
  while($n > 0){
    while($eof != "n"){
      if(!fseek($fp, $pos, SEEK_END)){
        $eof = fgetc($fp);
        $pos–;
        }else{
        break;
        }
      }
    $str .= fgets($fp);
    $eof = "";
    $n–;
    }
  return $str;
  }

echo nl2br(FileLastLines('sss.txt', 4));
/**
 * * * 取文件最后$n行 *
 * 
 * @param string $filename 文件路径 *
 * @param int $n 最后几行 *
 * @return mixed false表示有错误，成功则返回字符串
 */
function FileLastLines($filename, $n){
  if(!$fp = fopen($filename, 'r')){
    echo "打开文件失败，请检查文件路径是否正确，路径和文件名不要包含中文";
    return false;
    }
  $pos = -2;
  $eof = "";
  $str = "";
  while($n > 0){
    while($eof != "n"){
      if(!fseek($fp, $pos, SEEK_END)){
        $eof = fgetc($fp);
        $pos--;
        }else{
        break;
        }
      }
    $str .= fgets($fp);
    $eof = "";
    $n--;
    }
  return $str;
  }
echo nl2br(FileLastLines('sss . txt', 4));

function tail($fp, $n, $base = 5)
{
  assert($n > 0);
  $pos = $n + 1;
  $lines = array();
  while(count($lines) < = $n){
    try{
      fseek($fp, - $pos, SEEK_END);
      }
    catch (Exception $e){
      fseek(0);
      break;
      }
    $pos *= $base;
    while(!feof($fp)){
      array_unshift($lines, fgets($fp));
      }
    }
  return array_slice($lines, 0, $n);
  }
var_dump(tail(fopen("access.log", "r+"), 10));
$fp = fopen($file, "r");
$line = 10;
$pos = -2;
$t = " ";
$data = "";
while ($line > 0){
  while ($t != "n"){
    fseek($fp, $pos, SEEK_END);
    $t = fgetc($fp);
    $pos --;
    }
  $t = " ";
  $data .= fgets($fp);
  $line --;
  }
fclose ($fp);
echo $data;
&#63;>

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Readers can improve and improve it based on the characteristics of this example to make it more suitable for their own application needs.