Master PHP fwrite: Write Files Efficiently with Simple Code Examples

The fwrite() function in PHP provides a straightforward and flexible way to write data to files, a common requirement in many applications.

Syntax

fwrite(file, string, length)

Parameters

file

: Required. The file handle obtained from fopen(). string: Required. The data to write; can be a string, array, or other type (must be converted to a string). length: Optional. Maximum number of bytes to write; defaults to the length of the data.

Example: Writing a Simple String

<?php
$file = fopen("test.txt", "w"); // open file in write mode
if ($file) {
    $content = "Hello, World!"; // data to write
    fwrite($file, $content); // write data
    fclose($file); // close file
    echo "Write successful!";
} else {
    echo "Unable to open file!";
}
?>

This example opens test.txt for writing, writes the string "Hello, World!", closes the file, and outputs a success message.

Example: Writing an Array

<?php
$file = fopen("data.txt", "w");
if ($file) {
    $data = array("Zhang San", "Li Si", "Wang Wu");
    fwrite($file, serialize($data)); // serialize array before writing
    fclose($file);
    echo "Write successful!";
} else {
    echo "Unable to open file!";
}
?>

Here an array is serialized with serialize() to convert it into a string, then written to data.txt.

Important Notes

Open the file with a writeable mode such as "w" (write) or "a" (append).

Always verify that fopen() succeeded before calling fwrite().

Close the file with fclose() after writing to release resources.

When writing non‑string data, convert it to a string first (e.g., using serialize() or json_encode()).