Filesystem 函数
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feof

(PHP 4, PHP 5)

feof — 测试文件指针是否到了文件结束的位置

说明

bool feof ( resource $handle )

如果文件指针到了 EOF 或者出错时则返回 TRUE，否则返回一个错误（包括 socket 超时），其它情况则返回 FALSE。

Warning

如果服务器没有关闭由 fsockopen() 所打开的连接，feof() 会一直等待直到超时而返回 TRUE。默认的超时限制是 60 秒，可以使用 stream_set_timeout() 来改变这个值。

文件指针必须是有效的，必须指向由 fopen() 或 fsockopen() 成功打开的文件(并还未由 fclose() 关闭)。

Warning

如果传递的文件指针无效可能会陷入无限循环中，因为 EOF 不会返回 TRUE。

Example #1 使用无效文件指针的 feof() 例子

<?php
// 如果文件不可读取或者不存在，fopen 函数返回 FALSE
$file = @fopen("no_such_file", "r");

// 来自 fopen 的 FALSE 会发出一条警告信息并在这里陷入无限循环
while (!feof($file)) {
}

fclose($file);
?>

参数

handle

文件指针必须是有效的，必须指向由 fopen() 或 fsockopen() 成功打开的文件(并还未由 fclose() 关闭)。

返回值

Returns TRUE if the file pointer is at EOF or an error occurs (including socket timeout); otherwise returns FALSE.

注释

Warning

If a connection opened by fsockopen() wasn't closed by the server, feof() will hang. To workaround this, see below example:

Example #2 Handling timeouts with feof()

<?php
function safe_feof($fp, &$start = NULL) {
 $start = microtime(true);

 return feof($fp);
}

/* Assuming $fp is previously opened by fsockopen() */

$start = NULL;
$timeout = ini_get('default_socket_timeout');

while(!safe_feof($fp, $start) && (microtime(true) - $start) < $timeout)
{
 /* Handle */
}
?>

Warning

If the passed file pointer is not valid you may get an infinite loop, because feof() fails to return TRUE.

Example #3 feof() example with an invalid file pointer

<?php
// if file can not be read or doesn't exist fopen function returns FALSE
$file = @fopen("no_such_file", "r");

// FALSE from fopen will issue warning and result in infinite loop here
while (!feof($file)) {
}

fclose($file);
?>

Filesystem 函数
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PHP手册
PHP手册 - N: 测试文件指针是否到了文件结束的位置

用户评论:

dewi at dewimorgan dot com (10-Feb-2012 07:17)

Return values in the documentation are incorrectly stated. It says:

Returns TRUE if the file pointer is at EOF or an error occurs (including socket timeout); otherwise returns FALSE.

Correct text would be more like:

Returns FALSE if no filehandle was passed;
returns NULL if no filehandle was passed;
returns TRUE if the file pointer is at EOF or an error occurs (including socket timeout);
otherwise returns FALSE.

As an example, running the following from the commandline:

php -r 'echo
    "Empty: ".var_export(feof(), true)."\n".
    "Null: ".var_export(feof(NULL), true)."\n".
    "Undefined: ".var_export(feof($undef), true)."\n"
;'

This will output:

PHP Warning:  Wrong parameter count for feof() in Command line code on line 1
PHP Warning:  feof(): supplied argument is not a valid stream resource in Command line code on line 1
PHP Warning:  feof(): supplied argument is not a valid stream resource in Command line code on line 1

Empty: NULL
Null: false
Undefined: false

This can, as other commenters have reported, result in infinite loops and massive PHP error logfiles, if the file handle returned by fopen() is invalid for any reason.

kexianbin at diyism dot com (09-Jun-2010 09:16)

The forgotten function to detect if it is at the last line in many language:

<?php
function llof($fp) {
         {$p_current=ftell($fp);
          $rtn=fgets($fp)?false:true;
          fseek($fp, $p_current);
          return $rtn;
}
?>

sudo dot adam dot carruthers at gmail dot com (07-Feb-2010 05:01)

When using feof() on a TCP stream, i found the following to work (after many hours of frustration and anger):

NOTE: I used ";" to denote the end of data transmission.  This can be modified to whatever the server's end of file or in this case, end of output character is.

<?php
        $cursor = "";
        $inData = "";

        while(strcmp($cursor, ";") != 0) {
            $cursor = fgetc($sock);
            $inData.= $cursor;
        }
        fclose($sock);
        echo($inData);
?>

Since strcmp() returns 0 when the two strings are equal, it will return non zero as long as the cursor is not ";".  Using the above method will add ";" to the string, but the fix for this is simple.

<?php
        $cursor = "";
        $inData = "";

         $cursor = fgetc($sock);
        while(strcmp($cursor, ";") != 0) {
            $inData.= $cursor;
        }
        fclose($sock);
        echo($inData);
?>

I hope this helps someone.

jakicoll (03-Jan-2010 12:59)

Please note that feof() used with TCP-Connections, returns false as long as the connection is open.
It even returns false when there is no data available.

BTW: Using feof() with HTTP for a single request, you should always make sure that you set the HTTP-Header "Connection" to "close" and _not_ to "keep-alive".

honzam+php at ipdgroup dot com (28-Feb-2008 10:17)

Johannes: Remember note from stream_get_meta_data page: For socket streams this member [eof] can be TRUE  even when unread_bytes  is non-zero. To determine if there is more data to be read, use feof() instead of reading this item.

Another thing: better not rely on the "including socket timeout" part of when feof returns true. Just found program looping two days in while(!feof($fd)) fread ... with 20 seconds timeout in PHP 4.3.10.

Jet (19-Sep-2007 03:03)

To avoid infinite loop with fgets() just use do..while statement.

<?php
if ($f = fopen('myfile.txt', 'r')) do {
    $line = fgets($f);
    // do any stuff here...
} while (!feof($f));
fclose($f);

cmr at forestfactory dot de (19-Nov-2006 04:57)

Here's solution 3:

<?
$fp = fopen("myfile.txt", "r");
while ( ($current_line = fgets($fp)) !== false ) {
  // do stuff to the current line here
}
fclose($fp);
?>

AFAICS fgets() never returns an empty string, so we can also write:

<?
$fp = fopen("myfile.txt", "r");
while ( $current_line = fgets($fp) ) {
  // do stuff to the current line here
}
fclose($fp);
?>

Tom (24-Oct-2006 11:27)

feof() is, in fact, reliable.  However, you have to use it carefully in conjunction with fgets().  A common (but incorrect) approach is to try something like this:

<?
$fp = fopen("myfile.txt", "r");
while (!feof($fp)) {
  $current_line = fgets($fp);
  // do stuff to the current line here
}
fclose($fp);
?>

The problem when processing plain text files is that feof() will not return true after getting the last line of input.  You need to try to get input _and fail_ before feof() returns true.  You can think of the loop above working like this:

* (merrily looping, getting lines and processing them)
* fgets used to get 2nd to last line
* line is processed
* loop back up -- feof returns false, so do the steps inside the loop
* fgets used to get last line
* line is processed
* loop back up -- since the last call to fgets worked (you got the last line), feof still returns false, so you do the steps inside the loop again
* fgets used to try to get another line (but there's nothing there!)
* your code doesn't realize this, and tries to process this non-existent line (typically by doing the same actions again)
* now when your code loops back up, feof returns true, and your loop ends

There's two ways to solve this:

1. You can put an additional test for feof() inside the loop
2. You can move around your calls to fgets() so that the testing of feof() happens in a better location

Here's solution 1:

<?
$fp = fopen("myfile.txt", "r");
while(!feof($fp)) {
  $current_line = fgets($fp);
  if (!feof($fp)) {
    // process current line
  }
}
fclose($fp);
?>

And here's solution 2 (IMHO, more elegant):

<?
$fp = fopen("myfile.txt", "r");
$current_line = fgets($fp);
while (!feof($fp)) {
  // process current line
  $current_line = fgets($fp);
}
fclose($fp);
?>

FYI, the eof() function in C++ works the exact same way, so this isn't just some weird PHP thing...

ironoxid at libero dot it (06-Jun-2006 02:52)

I really thought that the feof() was TRUE when the logical file pointer is a EOF.
but no !
we need to read and get an empty record before the eof() reports TRUE.

So

$fp = fopen('test.bin','rb');
while(!feof($fp)) {
  $c = fgetc($fp);
  // ... do something with $c
  echo ftell($fp), ",";
}
echo 'EOF!';

prints for two time the last byte position.
If our file length is 5 byte this code prints

0,1,2,3,4,5,5,EOF!

Because of this, you have to do another check to verify if fgetc really reads another byte (to prevent error on "do something with $c" ^_^).

To prevent errors you have to use this code

$fp = fopen('test.bin','rb');
while(!feof($fp)) {
  $c = fgetc($fp);
  if($c === false) break;
  // ... do something with $c
}

but this is the same of

$fp = fopen('test.bin','rb');
while(($c = fgetc($fp))!==false) {
  // ... do something with $c
}

Consequently feof() is simply useless.
Before write this note I want to submit this as a php bug but one php developer said that this does not imply a bug in PHP itself (http://bugs.php.net/bug.php?id=35136&edit=2).

If this is not a bug I think that this need at least to be noticed.

Sorry for my bad english.
Bye ;)

m a p o p a at g m a i l. c o m (03-Jun-2006 01:58)

you  can avoid the infinite loop and filling the error logs
by an simple if statement
Here is the example

    $handle = fopen("http://xml.weather.yahoo.com/forecastrss?p=AYXX0008&u=f", "r");
    $xml = "";
    if ($handle)
    {
       while (!feof($handle))
       {
           $xml .= fread($handle, 128);
       }
        fclose($handle);
    }

(02-Jan-2006 02:27)

if you use fseek function to pos the pointer exceed the size the file,feof still return true.so note that when you use feof as the condition of while loop.

(01-Aug-2005 06:21)

if you hit an feof() infinite loop, watch out for resultant humongous logs, they can cripple a site with hard disk usage limits or run up excess usage fees.

(04-Mar-2005 05:02)

if you're worried the file pointer is invalid, TEST IT before you go into your loop... that way it'll never be an infinite loop.

Johannes (12-Mar-2004 10:47)

I found feof() to be a slow function when using a non-blocking connection.

The function stream_get_meta_data() returns much quicker and has a return field 'eof'.