PHP fwrite() Function: Syntax, Parameters, Usage, and Examples

The fwrite() function in PHP is used to write data to a file.

Function Syntax:

<code>int fwrite ( resource $handle , string $string [, int $length ] )</code>

Parameter Description:

handle : required. The file resource handle returned by fopen() .

string : required. The string to write to the file.

length : optional. Maximum number of bytes to write; if omitted, the entire string is written.

Return Value:

On success, returns the number of bytes written; on failure, returns false .

Usage of fwrite():

Open a File

Use fopen() to open a file and obtain a file resource handle, e.g.:

<code>$file = fopen("example.txt", "w");</code>

Write Data

Use fwrite() to write data to the file, e.g.:

<code>fwrite($file, "Hello, World!");</code>

This writes "Hello, World!" into the opened file.

Specify Number of Bytes

You can limit the number of bytes written with the optional $length parameter, e.g.:

<code>fwrite($file, "Hello, World!", 5);</code>

Only the first five characters "Hello" are written.

Check Write Success

Check the return value of fwrite() ; if it is false , the write failed:

<code>if (fwrite($file, "Hello, World!") === false) {
    echo "Write failed";
} else {
    echo "Write succeeded";
}</code>

Close the File

After writing, close the file with fclose() to release resources and ensure data is saved:

<code>fclose($file);</code>

Note that fwrite() overwrites existing content; to append, open the file in append mode ("a") and then use fwrite() to add data at the end.

Summary

The fwrite() function writes data to a file by opening it, writing with optional byte limits, checking success, and finally closing it. It can also be used in append mode to add data without overwriting.