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Last updated: Fri, 11 Apr 2008

fwrite

(PHP 4, PHP 5)

fwrite — Escritura sobre archivos, segura con material binario

Descripción

int fwrite ( resource $gestor , string $cadena [, int $longitud ] )

fwrite() escribe los contenidos de cadena a la secuencia de archivo apuntada por gestor .

Lista de parámetros

gestor

A file system pointer resource that is typically created using fopen().

cadena

La cadena a ser escrita.

longitud

Si el argumento longitud es entregado, la escritura se detendrá después de que longitud bytes hayan sido escritos, o al alcanzar el final de cadena , aquello que ocurra primero.

Note que si se utiliza el argumento longitud , entonces la opción de configuración magic_quotes_runtime será ignorada y no se eliminarán caracteres de barra en la cadena .

Valores retornados

fwrite() devuelve el número de bytes escritos, o FALSE en caso de fallo.

Notes

Note: En los sistemas que diferencian entre archivos binarios y de texto (es decir, Windows) el archivo debe ser abierto incluyendo el valor 'b' en el parámetro de modo de fopen().

Note: Si gestor fue abierto con fopen() en modo de adición, las escrituras con fwrite() son atómicas (a menos que el tamaño de cadena exceda el tamaño de bloque del sistema de archivos, en algunas plataformas, y siempre y cuando el archivo esté en un sistema de archivos local). Es decir, no es necesario usar flock() sobre un recurso antes de llamar fwrite(); todos los datos serán escritos sin interrupción.

Ejemplos

Example #1 Un ejemplo sencillo de fwrite()


<?php
$nombre_archivo = 'prueba.txt';
$contenido = "Agregar esto al archivo\n";

// Asegurarse primero de que el archivo existe y puede escribirse sobre él.
if (is_writable($nombre_archivo)) {

    // En nuestro ejemplo estamos abriendo $nombre_archivo en modo de adición.
    // El apuntador de archivo se encuentra al final del archivo, así que
    // allí es donde irá $contenido cuando llamemos fwrite().
    if (!$gestor = fopen($nombre_archivo, 'a')) {
         echo "No se puede abrir el archivo ($nombre_archivo)";
         exit;
    }

    // Escribir $contenido a nuestro arcivo abierto.
    if (fwrite($gestor, $contenido) === FALSE) {
        echo "No se puede escribir al archivo ($nombre_archivo)";
        exit;
    }

    echo "Éxito, se escribió ($contenido) al archivo ($nombre_archivo)";

    fclose($gestor);

} else {
    echo "No se puede escribir sobre el archivo $nombre_archivo";
}
?>

Ver también

glob

ftruncate

Last updated: Fri, 11 Apr 2008

add a note User Contributed Notes
fwrite

elinor_hust at REMOVETHIS dot hotmail dot com
01-Apr-2008 03:26


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
20-Feb-2008 07:47


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
15-Jan-2008 11:20


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
05-Sep-2007 07:13


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
29-Mar-2007 09:52


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 12:09


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 09:08


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 08:49


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 11:40


[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 05:09


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 06:02


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 02:25


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 03:24


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 09:15


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 06:55


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 08:27


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 06:56


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
27-Oct-2004 12:32


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
22-Aug-2003 12:04


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 11:32


[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 11:36


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 08:35


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 12:12


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 07:33


[[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

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Last updated: Fri, 11 Apr 2008