fwrite
(PHP 4, PHP 5, PHP 7, PHP 8)
fwrite — Binary-safe file write
Description
$stream
, string $data
, ?int $length
= null
): int|false
fwrite() writes the contents of
data
to the file stream pointed to by
stream
.
Parameters
-
stream
-
A file system pointer resource that is typically created using fopen().
-
data
-
The string that is to be written.
-
length
-
If
length
is an int, writing will stop afterlength
bytes have been written or the end ofdata
is reached, whichever comes first.
Return Values
fwrite() returns the number of bytes
written, or false
on failure.
Errors/Exceptions
fwrite() raises E_WARNING
on failure.
Changelog
Version | Description |
---|---|
8.0.0 |
length is nullable now.
|
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 $somecontent will go when we fwrite() it.
if (!$fp = fopen($filename, 'a')) {
echo "Cannot open file ($filename)";
exit;
}
// Write $somecontent to our opened file.
if (fwrite($fp, $somecontent) === FALSE) {
echo "Cannot write to file ($filename)";
exit;
}
echo "Success, wrote ($somecontent) to file ($filename)";
fclose($fp);
} else {
echo "The file $filename is not writable";
}
?>
Notes
Note:
Writing to a network stream may end before the whole string is written. Return value of fwrite() may be checked:
<?php
function fwrite_stream($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
stream
was fopen()ed in append mode, fwrite()s are atomic (unless the size ofdata
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.
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!
?>
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
- pack() - Pack data into binary string