ftruncate
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
?>
fwrite
(PHP 4, PHP 5)
fwrite — Binary-safe file write
Description
int fwrite
( resource
$handle
, string $string
[, int $length
] )
fwrite() writes the contents of
string to the file stream pointed to by
handle.
Parameters
-
handle -
A file system pointer resource that is typically created using fopen().
-
string -
The string that is to be written.
-
length -
If the
lengthargument is given, writing will stop afterlengthbytes have been written or the end ofstringis reached, whichever comes first.Note that if the
lengthargument is given, then the magic_quotes_runtime configuration option will be ignored and no slashes will be stripped fromstring.
Return Values
fwrite() returns the number of bytes
written, or FALSE on error.
Notes
Note:
Writing to a network stream may end before the whole string is written. Return value of fwrite() may be checked:
<?php
function fwrite_stream($fp, $string) {
for ($written = 0; $written < strlen($string); $written += $fwrite) {
$fwrite = fwrite($fp, substr($string, $written));
if ($fwrite === false) {
return $written;
}
}
return $written;
}
?>
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
handlewas fopen()ed in append mode, fwrite()s are atomic (unless the size ofstringexceeds 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.
Note:
If writing twice to the file pointer, then the data will be appended to the end of the file content:
<?php
$fp = fopen('data.txt', 'w');
fwrite($fp, '1');
fwrite($fp, '23');
fclose($fp);
// the content of 'data.txt' is now 123 and not 23!
?>
Examples
Example #1 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 $filename is not writable";
}
?>
See Also
- fread() - Binary-safe file read
- fopen() - Opens file or URL
- fsockopen() - Open Internet or Unix domain socket connection
- popen() - Opens process file pointer
- file_get_contents() - Reads entire file into a string
add a note
User Contributed Notes
fwrite - [34 notes]
MKP Dev ¶
7 years ago
Andi ¶
9 years ago
[Ed. Note:
The runtime configuration setting auto_detect_line_endings should solve this problem when set to On.]
I figured out problems when writing to a file using \r as linebreak, after that file() wasn't able to read the data from that file.
Using \n solved the problem.
dharris dot nospam at removethispart dot drh dot net ¶
5 years ago
Some people say that when writing to a socket not all of the bytes requested to be written may be written. You may have to call fwrite again to write bytes that were not written the first time. (At least this is how the write() system call in UNIX works.)
This is helpful code (warning: not tested with multi-byte character sets)
function fwrite_with_retry($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");
chill at cuna dot org ¶
8 years ago
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";
}
Anonymous ¶
3 years ago
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.
chad 0x40 herballure 0x2e com ¶
5 years ago
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.
bahatest at ifrance doc com ¶
7 years ago
[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("éaè!");
// adding header
$text="\xEF\xBB\xBF".$text;
fputs($f, $text);
fclose($f);
?>
kzevian at cybercable dot net dot mx ¶
8 years ago
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 ¶
8 years ago
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)
Jake Roberts ¶
9 years ago
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($fh)) ) die "Error Reading";
Thus it will be successful on reading zero bytes but detect and error returned as FALSE.
nate at frickenate dot com ¶
3 years ago
After having problems with fwrite() returning 0 in cases where one would fully expect a return value of false, I took a look at the source code for php's fwrite() itself. The function will only return false if you pass in invalid arguments. Any other error, just as a broken pipe or closed connection, will result in a return value of less than strlen($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;
}
?>
chedong at hotmail dot com ¶
9 years ago
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));
Jon Haynes ¶
2 years ago
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.
oktavianus dot programmer at gmail dot com ¶
3 years ago
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
michael at newbcity dot com ¶
4 years ago
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";
//}
?>
elinor_hust at REMOVETHIS dot hotmail dot com ¶
5 years ago
Remember to use double-quotes when outputting special characters such as \n or they come out literally.
...
james at nicolson dot biz ¶
7 years ago
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 $count;
}
?>
pubdc on yahoo ¶
1 year ago
I have encountered many instances where fwrite will fail to append all text to the file, especially when there is a sequence of fwrite appends.
Sometimes it will work fine, sometimes the file will be only half-written. Adding a usleep(100000) for a tenth-of-a-second pause between the fwrites will usually avoid such issues without imposing too much of a delay.
james at facepwn dot com ¶
4 years ago
if (is_writable($filename)) {
Could also be
if (is_writable($filename) or die ("Can not write to ".$filename)) {
cutmaster at fearlesss dot com ¶
6 years ago
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 ç");
$fh=fopen('test.xml',"w");
fwrite($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 ç";
$fh=fopen('test.xml',"w");
fwrite($fh,utf8_encode($myString));
fclose($fh);
?>
Hope this will help
ceo at l-i-e dot com ¶
4 years ago
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
mesho ¶
5 years ago
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);
?>
albert;cutthis; at ;coznospam;ribox dot nl ¶
7 years ago
To write 'true binary' files combine with pack() :
$a = 65530;
$fp = fopen('test.dat', 'w');
fwrite($fp, pack('L', $a));
fclose($fp);
Will at EnigmaChannel dot com ¶
8 years ago
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 ¶
8 years ago
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 ¶
8 years ago
if you want to create quickly and without fopen use system, exec
system('echo "blahblah" > /path/file');
php at biggerthanthebeatles dot com ¶
9 years ago
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,$batch_data);
The is the equivalent of opening a txt file in notepad pressing enter and the end of the line and saving it.
Chris Blown ¶
9 years ago
Don't forget to check fwrite returns for errors! Just because you successfully opened a file for write, doesn't always mean you can write to it.
On some systems this can occur if the filesystem is full, you can still open the file and create the filesystem inode, but the fwrite will fail, resulting in a zero byte file.
chaobreederxl at gmail dot com ¶
6 years ago
This is a simple function I wrote that uses the fopen and fwrite functions to log the actions of users... very useful for tracking your members on your site.
<?php
function loguser($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
zaccraven at junk.com ¶
6 years ago
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 $tmp.
Credit for this goes to someone called Eugene Murai, I found this solution by him after searching for several hours.
santibari at yahoo dot com ¶
7 years ago
To write a specific byte into a file (let's,say 0000 0001), use the function chr().
<?php
fputs($fp,chr(0x01),1);
?>
seeker at seek dot planet ¶
10 years ago
[[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.
chaly ¶
3 years ago
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 $ret;
}
?>
kontakt at bmservices dot de ¶
4 years ago
Checking if fwrite failed will not work in that way:
if (!fwrite($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, Gérôme