PHP fputs Function
last modified April 3, 2025
The PHP fputs function writes data to a file. It's identical to
fwrite and provides low-level file writing capabilities.
Basic Definition
The fputs function writes a string to a file pointer. It takes
three parameters: the file handle, the string to write, and optional length.
Syntax: fputs(resource $handle, string $string, int $length = ?): int.
It returns the number of bytes written or false on failure.
Basic fputs Example
This shows the simplest usage of fputs to write to a file.
<?php
declare(strict_types=1);
$file = fopen("output.txt", "w");
if ($file) {
$bytes = fputs($file, "Hello, World!");
fclose($file);
echo "Wrote $bytes bytes to file.";
}
This writes "Hello, World!" to output.txt. Always check if fopen succeeded and remember to close the file with fclose when done.
Appending to a File
Use the "a" mode to append content to an existing file.
<?php
declare(strict_types=1);
$file = fopen("log.txt", "a");
if ($file) {
$message = date('Y-m-d H:i:s') . " - User logged in\n";
fputs($file, $message);
fclose($file);
}
This appends a timestamped message to log.txt. The "a" mode creates the file if it doesn't exist and preserves existing content.
Writing Binary Data
fputs can write binary data when using the "b" mode flag.
<?php
declare(strict_types=1);
$file = fopen("data.bin", "wb");
if ($file) {
$binaryData = pack('C*', 0x48, 0x65, 0x6C, 0x6C, 0x6F);
$bytes = fputs($file, $binaryData);
fclose($file);
echo "Wrote $bytes bytes of binary data.";
}
This writes binary data (ASCII codes for "Hello") to a file. The "b" mode ensures proper handling of binary data across platforms.
Writing with Length Limit
The optional length parameter limits how many bytes are written.
<?php
declare(strict_types=1);
$file = fopen("partial.txt", "w");
if ($file) {
$text = "This is a long string that will be truncated";
$bytes = fputs($file, $text, 10);
fclose($file);
echo "Wrote first $bytes characters: " . substr($text, 0, 10);
}
This writes only the first 10 bytes of the string. The length parameter is useful when you need to write fixed-size chunks of data.
Error Handling
Proper error handling ensures robustness when writing files.
<?php
declare(strict_types=1);
$file = @fopen("readonly.txt", "w");
if ($file === false) {
die("Failed to open file");
}
$result = fputs($file, "Attempt to write");
if ($result === false) {
echo "Failed to write to file";
} else {
echo "Successfully wrote $result bytes";
}
fclose($file);
This shows proper error checking for both file opening and writing. The @ suppresses warnings, allowing custom error handling.
Best Practices
- Check Returns: Always verify fputs return value.
- Proper Modes: Use correct file opening modes.
- Resource Cleanup: Always close files with fclose.
- Error Handling: Implement comprehensive error checking.
- Binary Safety: Use "b" mode for binary data.
Source
This tutorial covered the PHP fputs function with practical
examples showing its usage in different scenarios.