fwrite

pubdc on yahoo (2011-10-18 23:48:29)

I have encountered many instances where fwrite will fail to append all text to the file, especially when there is a sequence of fwrite appends.
Sometimes it will work fine, sometimes the file will be only half-written. Adding a usleep(100000) for a tenth-of-a-second pause between the fwrites will usually avoid such issues without imposing too much of a delay.

Jon Haynes (2011-04-01 02:48:06)

Be careful of using reserved Windows filenames in fwrite operations.

<?php
$fh = fopen('prn.txt', 'w');
fwrite($fh, 'wtf?');
echo 'done' . PHP_EOL;
?>

The above script will hang (tested on Windows 7) before it can echo 'done'.

This is due to another 'feature' of our favourite operating system where filenames like prn.xxx, con.xxx, com1.xxx and aux.xxx (with xxx being any filename extension) are Windows reserved device names. Attempts to create/read/write to these files hangs the interpreter.

nate at frickenate dot com (2010-03-24 09:51:46)

After having problems with fwrite() returning 0 in cases where one would fully expect a return value of false, I took a look at the source code for php's fwrite() itself. The function will only return false if you pass in invalid arguments. Any other error, just as a broken pipe or closed connection, will result in a return value of less than strlen($string), in most cases 0.

Therefore, looping with repeated calls to fwrite() until the sum of number of bytes written equals the strlen() of the full value or expecting false on error will result in an infinite loop if the connection is lost.

This means the example fwrite_stream() code from the docs, as well as all the "helper" functions posted by others in the comments are all broken. You *must* check for a return value of 0 and either abort immediately or track a maximum number of retries.

Below is the example from the docs. This code is BAD, as a broken pipe will result in fwrite() infinitely looping with a return value of 0. Since the loop only breaks if fwrite() returns false or successfully writes all bytes, an infinite loop will occur on failure.

<?php
// BROKEN function - infinite loop when fwrite() returns 0s
function fwrite_stream($fp, $string) {
    for ($written = 0; $written < strlen($string); $written += $fwrite) {
        $fwrite = fwrite($fp, substr($string, $written));
        if ($fwrite === false) {
            return $written;
        }
    }
    return $written;
}
?>

chaly (2009-12-12 08:47:31)

Here are the two function I use to save my arrays to a file and load them into exactly the same array as it was before.

At the moment I have no need in saving ressources or something. There I guess a memory-dump and -load is needed.

<?php
    function save_array_to_file($filename,$b)
    {
        if (!is_resource($filename)) 
        {
            if (!$file = fopen($filename,'w+')) return false;
        } else {
            $file = $filename;
        }
        foreach ($b as $key=>$val)
        {
            fwrite($file,(is_int($key) ? chr(6).(string)$key : chr(5).$key));
            if (is_array($val))
            {
                fwrite($file,chr(0)); //array starts
                save_array_to_file($file,$val);
                fwrite($file,chr(1)); //array ends
            } 
            elseif (is_int($val)) 
            {
                fwrite($file,chr(2).(string) $val); //int
            } 
            elseif (is_string($val)) 
            {
                fwrite($file,chr(3).$val); //string
            }
        }
        if (!is_resource($filename)) fclose($file);
        return true;
    }
    function read_array_from_file($filename)
    {
        if (!is_resource($filename))
        {
            if (!$file = fopen($filename,'r')) return false;
        } else {
            $file = $filename;
        }
        $ret=array();
        $key='';
        $val=null;
        $mod=0;
        while (!feof($file))
        {
            $b = fread($file,1);
            if (ord($b) < 9) 
            {
                if ($val!=null)
                {
                    if ($mod==2) $val=(int) $val;
                    if ($mod==3) $val=(string) $val;
                    $ret[$key]=$val;
                    $key='';
                    $val=null;
                    $mod=0; 
                } else {
                    if (ord($b)==0)
                        $mod=0;
                    elseif (ord($b)==1)
                        return $ret;
                    else
                    {
                        if ($mod==5) $key=(string) $key;
                        if ($mod==6) $key=(int) $key;
                        $mod=ord($b);
                    }
                }
            } else {
                if ($mod==5 || $mod==5)
                    $key.=$b;
                elseif ($mod==0)
                    $val=read_array_from_file($file);
                else
                    $val.=$b;
            }
        }
        if (!is_resource($filename)) fclose($file);
        return $ret;
    }
?>

oktavianus dot programmer at gmail dot com (2009-06-03 20:51:55)

this the another sample to use fwrite with create a folder and create the txt file.

<?php
$mypath="testdir\\subdir\\test";
mkdir($mypath,0777,TRUE);
$filename = $mypath.'\test.txt';
$handle = fopen($filename,"x+");
$somecontent = "Add this to the file Oktavianus";
fwrite($handle,$somecontent);
echo "Success";
fclose($handle);
?> 

please try...
Oktavianus

Anonymous (2009-05-15 09:36:07)

If you write with the pointer in the middle of a file, it overwrites what's there rather than shifting the rest of the file along.

ceo at l-i-e dot com (2008-11-10 15:07:37)

If you are trying to write binary/structured data (e.g., a 4-byte sequence for an (int)) to a file, you will need to use:
http://php.net/pack

james at facepwn dot com (2008-10-09 17:25:12)

if (is_writable($filename)) {
Could also be
if (is_writable($filename) or die ("Can not write to ".$filename)) {

michael at newbcity dot com (2008-05-27 11:11:26)

For my fellow newbies, if you test the sample script and want to have the .txt file created for you, you need to comment out the is_writable stuff, like this:  

<?php
$filename = 'test.txt';
$somecontent = "Add this to the file\n";

// Let's make sure the file exists and is writable first.
//if (is_writable($filename)) {

// In our example we're opening $filename in append mode.
// The file pointer is at the bottom of the file hence
// that's where $somecontent will go when we fwrite() it.
if (!$handle = fopen($filename, 'a')) {
echo "Cannot open file ($filename)";
exit;
}

// Write $somecontent to our opened file.
if (fwrite($handle, $somecontent) === FALSE) {
echo "Cannot write to file ($filename)";
exit;
}

echo "Success, wrote ($somecontent) to file ($filename)";

fclose($handle);

//} else {
//echo "The file $filename is not writable";
//}
?>

kontakt at bmservices dot de (2008-05-22 04:03:03)

Checking if fwrite failed will not work in that way:
if (!fwrite($fH, $myText)) echo "Write error";
because fwrite return the number of bytes written or FALSE in case of an error.
So: if $myText is an empty string, fwrite will return 0, which is interpreted here as "FALSE", although the writing out of the string is ok.
So you should check in that way:
if (@fwrite($fH, $myText)===FALSE) echo "Write error";
Regards from Berlin, Gér?me

elinor_hust at REMOVETHIS dot hotmail dot com (2008-04-01 05:26:13)

Remember to use double-quotes when outputting special characters such as \n or they come out literally.
...

dharris dot nospam at removethispart dot drh dot net (2008-02-20 10:47:02)

Some people say that when writing to a socket not all of the bytes requested to be written may be written. You may have to call fwrite again to write bytes that were not written the first time. (At least this is how the write() system call in UNIX works.)
This is helpful code (warning: not tested with multi-byte character sets)
function fwrite_with_retry($sock, &$data)
{
$bytes_to_write = strlen($data);
$bytes_written = 0;
while ( $bytes_written < $bytes_to_write )
{
if ( $bytes_written == 0 ) {
$rv = fwrite($sock, $data);
} else {
$rv = fwrite($sock, substr($data, $bytes_written));
}
if ( $rv === false || $rv == 0 )
return( $bytes_written == 0 ? false : $bytes_written );
$bytes_written += $rv;
}
return $bytes_written;
}
Call this like so:
$rv = fwrite_with_retry($sock, $request_string);
if ( ! $rv )
die("unable to write request_string to socket");
if ( $rv != strlen($request_string) )
die("sort write to socket on writing request_string");

mesho (2008-01-15 02:20:48)

be easy :)), this works fine

<?

$file = "counter.txt";

if ( !file_exists($file)){
        touch ($file);
        $handle = fopen ($file, 'r+'); 
        $str = "<? \$count=0 ?>";

}
else{
        include "counter.txt";
        $count++;
        $str = "<? \$count=".$count." ?>";
        $handle = fopen ($file, 'r+'); 
}

fwrite ($handle, $str); 
fclose ($handle); 

?>

chad 0x40 herballure 0x2e com (2007-09-05 10:13:14)

Remember to check the return value of fwrite(). In particular, writing into a socket can return fewer bytes than requested, and you'll have to try again with the remainder of your data.

chaobreederxl at gmail dot com (2007-03-29 11:52:57)

This is a simple function I wrote that uses the fopen and fwrite functions to log the actions of users... very useful for tracking your members on your site. 

 <?php
 function loguser($reason,$ext = "db"){
  if(!is_dir("logs")):
   mkdir("logs","0493");
 endif;
  $fp = fopen("logs/".date("m-d-y").".".$ext, "a+");
   fwrite($fp, "<strong>".date("g:i:s A")."</strong>: ".$reason."<br/>");
 }
?>

To use this, just call the function like so:

<? loguser($_SERVER["REMOTE_ADDR"]." attempted to create another account.","html"); ?>

The second parameter can be changed to anything that would support HTML. If you leave out the second extension, then it automatically uses the .db extension, which works excellent for me. 

Hope this helps.

Paul

cutmaster at fearlesss dot com (2007-03-09 03:09:59)

For those who, like me, lost a lot of minutes (hours) to understand why fwrite doesn't create a real utf-8 file, here's the explanation I've found :

I tried to do something like this :
<?php
$myString = utf8_encode("Test with accents éèà?");
$fh=fopen('test.xml',"w");
fwrite($fh,$myString);
fclose($fh);
?>

For a mysterious reason, the resulted file shows the accent without the utf-8 conversion.

I tried the binary, mode, etc. etc. And finally I've found it :
It seems that fwrite NEEDS to have the utf8_encode function INSIDE its parameters like this, to understand it must create a non-text only file :
<?php
$myString = "Test with accents éèà?";
$fh=fopen('test.xml',"w");
fwrite($fh,utf8_encode($myString));
fclose($fh);
?>
Hope this will help

zaccraven at junk.com (2006-09-11 00:08:40)

Use this to get a UTF-8 Unicode CSV file that opens properly in Excel:
$tmp = chr(255).chr(254).mb_convert_encoding( $tmp, 'UTF-16LE', 'UTF-8');
$write = fwrite( $filepath, $tmp );
Use a tab character, not comma, to seperate the fields in the $tmp.
Credit for this goes to someone called Eugene Murai, I found this solution by him after searching for several hours.

santibari at yahoo dot com (2006-03-18 11:49:30)

To write a specific byte into a file (let's,say 0000 0001), use the function chr().
<?php

fputs($fp,chr(0x01),1);

?>

bahatest at ifrance doc com (2005-07-23 14:40:09)

[Editor's Note: No, you only need to use this if you want a BOM (Byte order mark) added to the document - most people do not.]

if you have to write a file in UTF-8 format, you have to add an header to the file like this :

<?php
$f=fopen("test.txt", "wb");
$text=utf8_encode("?a?!");
// adding header
$text="\xEF\xBB\xBF".$text;
fputs($f, $text);
fclose($f);
?>

james at nicolson dot biz (2005-07-06 08:09:22)

I could'nt quite get MKP Dev hit counter to work.... this is how I modified it
<?
function hitcount()
{
$file = "counter.txt";
if ( !file_exists($file)){
        touch ($file);
        $handle = fopen ($file, 'r+'); // Let's open for read and write
        $count = 0;

}
else{
        $handle = fopen ($file, 'r+'); // Let's open for read and write
        $count = fread ($handle, filesize ($file));
        settype ($count,"integer");
}
rewind ($handle); // Go back to the beginning
/*
 * Note that we don't have problems with 9 being fewer characters than
  * 10 because we are always incrementing, so we will always write at
   * least as many characters as we read
    **/
fwrite ($handle, ++$count); // Don't forget to increment the counter
fclose ($handle); // Done 

return $count;
}      
?>

albert;cutthis; at ;coznospam;ribox dot nl (2005-06-07 09:02:14)

To write 'true binary' files combine with pack() :
$a = 65530;
$fp = fopen('test.dat', 'w');
fwrite($fp, pack('L', $a));
fclose($fp);

MKP Dev (2005-05-12 05:25:11)

bluevd at gmail dot com mentioned a hit counter. In his/her implementation, the file is first opened, read, closed, then opened +truncated, then written, and closed again. An alternative to this is:
<?php
$file = 'counter.txt or whatever';
$handle = fopen ($file, 'r+'); // Let's open for read and write
$count = int (fread ($handle, filesize ($file)));
// We don't want to think it's a string and try appending
echo "Number of hits $count";
rewind ($handle); // Go back to the beginning
/*
 * Note that we don't have problems with 9 being fewer characters than
 * 10 because we are always incrementing, so we will always write at
 * least as many characters as we read
 **/
fwrite ($handle, ++$count); // Don't forget to increment the counter
fclose ($handle); // Done
?>

Will at EnigmaChannel dot com (2005-03-25 06:24:16)

Using fwrite to write to a file in your include folder...

PHP does not recognise the permissions setting for the file until you restart the server... this script works fine. (still have to create the blank text file first though...it is not created automatically) On OS X Server..
Using the 1 in fopen tells php to look for the file in your include folder. Change your include folder by altering include_path in php.ini
On OS X Server, php.ini is in private/etc/php.ini.default
copy the file and call it php.ini

the default include path is usr/lib/php
(All these folders are hidden - use TinkerTool to reveal them)

<?php
$file = fopen('textfile.txt', 'a', 1);
$text="\n Your text to write \n ".date('d')."-".date('m')."-".date('Y')."\n\n";
fwrite($file, $text); 
fclose($file);
?>

goodwork at myrealbox dot com (2005-02-17 12:15:37)

difficulty appending to file in SAFE MODE ON
if you are getting resource errors etc try this...
$textline="whatever string you submitted or created";
$filename="afilename.log"; // or whatever your path and filename
if (!$handle = fopen($filename, 'a')) {
echo "Cannot open file ($filename)"; // or handle your error
exit; }
$textline.="\n"; // dont forget that period
// now write content to our opened file.
IF (fwrite($handle,$textline) === FALSE)
{echo "Cannot write to file ($filename)";// or handle your error
exit;}
echo "Success, wrote ($textline) to file ($filename)";
fclose($handle);

sheyh (2005-02-09 21:55:12)

if you want to create quickly and without fopen use system, exec
system('echo "blahblah" > /path/file');

kzevian at cybercable dot net dot mx (2005-02-03 11:27:11)

I needed to append, but I needed to write on the file's beginning, and after some hours of effort this worked for me:
$file = "file.txt";
if (!file_exists("file.txt")) touch("file.txt");
$fh = fopen("file.txt", "r");
$fcontent = fread($fh, filesize("file.txt"));
$towrite = "$newcontent $fcontent";
$fh22 = fopen('file.txt', 'w+');
fwrite($fh2, $towrite);
fclose($fh);
fclose($fh2);

bluevd at gmail dot com (2004-12-22 09:56:08)

Watch out for mistakes in writting a simple code for a hit counter:
<?php
$cont=fopen('cont.txt','r');
$incr=fgets($cont);
//echo $incr;
$incr++;
fclose($cont);
$cont=fopen('cont.txt','a');
fwrite($cont,$incr);
fclose($cont);
?>

Why? notice the second fopen -> $cont=fopen('cont.txt','a');
it opens the file in writting mode (a). And when it ads the incremented
value ( $incr ) it ads it ALONG the old value... so opening the counter
page about 5 times will make your hits number look like this
012131214121312151.21312141213E+ .... you get the piont.
nasty, isn't it? REMEMBER to open the file with the 'w' mode (truncate
the file to 0). Doing this will clear the file content and it will make sure that
your counter works nice. This is the final code

<?php
$cont=fopen('cont.txt','r');
$incr=fgets($cont);
//echo $incr;
$incr++;
fclose($cont);
$cont=fopen('cont.txt','w');
fwrite($cont,$incr);
fclose($cont);
?>

Notice that this work fine =)
XU (alias Iscu Andrei)

chill at cuna dot org (2004-10-26 15:32:40)

In PHP 4.3.7 fwrite returns 0 rather than false on failure.
The following example will output "SUCCESS: 0 bytes written" for existing file test.txt:
$fp = fopen("test.txt", "rw");
if (($bytes_written = fwrite($fp, "This is a test")) === false) {
echo "Unable to write to test.txt\n\n";
} else {
echo "SUCCESS: $bytes_written bytes written\n\n";
}

php at biggerthanthebeatles dot com (2003-08-21 15:04:53)

Hope this helps other newbies.
If you are writing data to a txt file on a windows system and need a line break. use \r\n . This will write hex OD OA.
i.e.
$batch_data= "some data... \r\n";
fwrite($fbatch,$batch_data);
The is the equivalent of opening a txt file in notepad pressing enter and the end of the line and saving it.

Andi (2003-07-17 02:32:39)

[Ed. Note:
The runtime configuration setting auto_detect_line_endings should solve this problem when set to On.]
I figured out problems when writing to a file using \r as linebreak, after that file() wasn't able to read the data from that file.
Using \n solved the problem.

chedong at hotmail dot com (2003-06-20 02:36:23)

the fwrite output striped the slashes if without length argument given, example:

<?php
$str = "c:\\01.txt";
$out = fopen("out.txt", "w");
fwrite($out, $str);
fclose($out);
?>

the out.txt will be:
c:^@1.txt
the '\\0' without escape will be '\0' ==> 0x00.

the correct one is change fwrite to:
fwrite($out, $str, strlen($str));

Jake Roberts (2003-06-04 11:35:09)

Use caution when using:
$content = fread($fh, filesize($fh)) or die "Error Reading";
This will cause an error if the file you are reading is zero length.
Intead use:
if ( false === fread($fh, filesize($fh)) ) die "Error Reading";
Thus it will be successful on reading zero bytes but detect and error returned as FALSE.

Chris Blown (2003-05-19 03:12:36)

Don't forget to check fwrite returns for errors! Just because you successfully opened a file for write, doesn't always mean you can write to it.
On some systems this can occur if the filesystem is full, you can still open the file and create the filesystem inode, but the fwrite will fail, resulting in a zero byte file.

seeker at seek dot planet (2003-02-09 22:33:05)

[[Editors note: There is no "prepend" mode, you must essentially rewrite the entire file after prepending contents to a string. Perhaps you will use file(), modify, implode(), then fopen()/fwrite() it back]]
To put strings into the front of the file, you need to set place the pointer at the top of the file when openning the file with fopen(), see fopen() for more info.