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Last updated: Fri, 01 Jun 2007

fwrite

(PHP 4, PHP 5)

fwrite — Binary-safe file write

Description

int fwrite ( resource $handle, string $string [, int $length] )

fwrite() writes the contents of string to the file stream pointed to by handle. If the length argument is given, writing will stop after length bytes have been written or the end of string is reached, whichever comes first.

fwrite() returns the number of bytes written, or FALSE on error.

Note that if the length argument is given, then the magic_quotes_runtime configuration option will be ignored and no slashes will be stripped from string.

Note: On systems which differentiate between binary and text files (i.e. Windows) the file must be opened with 'b' included in fopen() mode parameter.

Note: If handle was fopen()ed in append mode, fwrite()s are atomic (unless the size of string exceeds the filesystem's block size, on some platforms, and as long as the file is on a local filesystem). That is, there is no need to flock() a resource before calling fwrite(); all of the data will be written without interruption.

Example 636. A simple fwrite() example


<?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";

}

?>

See also fread(), fopen(), fsockopen(), popen(), and file_put_contents().

add a note User Contributed Notes
fwrite

chaobreederxl at gmail dot com
29-Mar-2007 07:52


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
09-Mar-2007 11:09


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 éèàç");


$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 éèàç";


$fh=fopen('test.xml',"w");


fwrite($fh,utf8_encode($myString));


fclose($fh);


?>


Hope this will help

zaccraven at junk.com
11-Sep-2006 07:08


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
18-Mar-2006 07:49


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
23-Jul-2005 09:40


[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
06-Jul-2005 03:09


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
07-Jun-2005 04:02


To write 'true binary' files combine with pack() :



$a = 65530;

$fp = fopen('test.dat', 'w');

fwrite($fp, pack('L', $a));

fclose($fp);

MKP Dev
12-May-2005 12:25


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
25-Mar-2005 02:24


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
17-Feb-2005 08:15


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
10-Feb-2005 05:55


if you want to create quickly and without fopen use system, exec



system('echo "blahblah" > /path/file');

kzevian at cybercable dot net dot mx
03-Feb-2005 07:27


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
22-Dec-2004 05:56


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
26-Oct-2004 10:32


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
21-Aug-2003 10:04


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
17-Jul-2003 09:32


[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
20-Jun-2003 09:36


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
04-Jun-2003 06:35


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
19-May-2003 10:12


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
10-Feb-2003 06:33


[[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.

add a note

glob

ftruncate

Last updated: Fri, 01 Jun 2007