fwrite()

fwrite() — Binary-safe file write.

Built-in function of PHP 8.5. The manual lists it as available in PHP 4, PHP 5, PHP 7, PHP 8. This page is the reference card: signature, parameters and return value, plus the changelog and the example the manual provides.

What it does

fwrite() writes the contents of data to the file stream pointed to by stream.

Signature

fwrite(resource $stream, string $data, ?int $length = null): int|false

Parameters

Parameter	Type	What it takes
$stream	resource	A file system pointer resource that is typically created using fopen().
$data	string	The string that is to be written.
$length	?int	If length is an int, writing will stop after length bytes have been written or the end of data is reached, whichever comes first.

Return value

fwrite() returns the number of bytes written, or false on failure.

Example

A runnable snippet:

$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"; }

Changelog

Version	Change
8.0.0	length is nullable now.