CODEWITHSUNDEEP
phpfopenfwritefilesizefread
nttaylor
nttaylor

Reputation: 828

weird PHP filesize behavior

In the code below I...

  1. open a textfile, write four characters to it, and close it again,

  2. re-open it, read the contents, and use filesize to report the size of the file. (It's 4, as it should be),

  3. manipulate those contents and tack on four more characters as well. Then I write that new string to the textfile and close it again,

  4. use filesize again to report how big the file is.

To my surprise, the answer it gives is still 4 even though the actual size of the file is 8! Examining the contents of the file proves that the write works and the length of the contents is 8.

What is going on??

By the way I have to use fread and fwrite instead of file_get_contents and file_put_contents. At least I think I do. This little program is a stepping stone to using "flock" so I can read the contents of a file and rewrite to it while making sure no other processes use the file in between. And AFAIK flock doesn't work with file_get_contents and file_put_contents.

Please help!

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

// Write 4 characters
$fp = fopen($filename, "w");
fwrite($fp, "1234");
fclose($fp);

// read those characters, manipulate them, and write them back (also increasing filesize).
$fp = fopen($filename, "r+");
$size = filesize($filename);
echo "size before is: " . $size . "<br>";
$t = fread($fp, $size);
$t = $t[3] . $t[2] . $t[1] . $t[0] . "5678";
rewind($fp);
fwrite($fp, $t);
fclose($fp);

// "filesize" returns the same number as before even though the file is larger now.
$size = filesize($filename);
echo "size after is: " . $size . "   ";

?>

Upvotes: 0

Views: 2206

Answers (3)

Kinga the Witch
Kinga the Witch

Reputation: 129

Note that cached value is used only in current script. When you run the script again filesize() reads new (proper) size of file. Example:

$filename='blahdeeblah.txt';

$fp=fopen($filename, 'a');

$size=@filesize($filename);
echo 'Proper size: '.$size.'<br>';

fwrite($fp, '1234');
fclose($fp);

$size=@filesize($filename);
echo 'Wrong size: '.$size;

Upvotes: 0

Kinga the Witch
Kinga the Witch

Reputation: 129

When you open a file by fopen() function you can obtain proper size at any time using fstat() function:

$fstat=fstat($fp);
echo 'Size: '.$fstat['size'];

Example:

$filename='blahdeeblah.txt';

$fp=fopen($filename, 'a');

$size=@filesize($filename);
echo 'Proper size (obtained by filesize): '.$size.'<br>';

$fstat=fstat($fp);
echo 'Proper size (obtained by fstat): '.$fstat['size'].'<br><br>';

fwrite($fp, '1234');
echo 'Writing 4 bytes...<br><br>';

$fstat=fstat($fp);
echo 'Proper size (obtained by fstat): '.$fstat['size'].'<br>';

fclose($fp);

$size=@filesize($filename);
echo 'Wrong size (obtained by filesize): '.$size;

Upvotes: 1

CJ Dennis
CJ Dennis

Reputation: 4336

From http://php.net/manual/en/function.filesize.php

Note: The results of this function are cached. See clearstatcache() for more details.

Upvotes: 3

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