PHP file_put_contents Function
last modified April 3, 2025
The PHP file_put_contents function writes data to a file. It's a
simple way to create or overwrite files in one function call.
Basic Definition
The file_put_contents function writes a string to a file. It can
create the file if it doesn't exist. The function returns the number of bytes
written or false on failure.
Syntax: file_put_contents(string $filename, mixed $data, int $flags = 0, ?resource $context = null): int|false.
Basic file_put_contents Example
This shows the simplest usage of file_put_contents to write text.
<?php
declare(strict_types=1);
$file = 'example.txt';
$data = 'Hello, World!';
$result = file_put_contents($file, $data);
if ($result !== false) {
echo "Successfully wrote $result bytes to $file";
} else {
echo "Failed to write to $file";
}
This creates or overwrites example.txt with "Hello, World!". The function returns the number of bytes written or false on error.
Appending to a File
Use the FILE_APPEND flag to add content without overwriting existing data.
<?php
declare(strict_types=1);
$file = 'log.txt';
$data = "New log entry at " . date('Y-m-d H:i:s') . PHP_EOL;
$result = file_put_contents($file, $data, FILE_APPEND);
if ($result !== false) {
echo "Appended $result bytes to $file";
} else {
echo "Failed to append to $file";
}
This appends a timestamped log entry to log.txt. The FILE_APPEND flag preserves existing content. PHP_EOL adds the correct end-of-line character.
Writing Arrays to File
You can write array data by converting it to a string first.
<?php
declare(strict_types=1);
$file = 'data.csv';
$data = ['Name', 'Email', 'Phone'];
$csv = implode(',', $data) . PHP_EOL;
$result = file_put_contents($file, $csv);
if ($result !== false) {
echo "Wrote CSV header with $result bytes";
} else {
echo "Failed to write CSV data";
}
This converts an array to a CSV string and writes it to a file. implode joins array elements with commas. Always validate and sanitize array data first.
Locking Files During Write
Use LOCK_EX to prevent other processes from writing to the file simultaneously.
<?php
declare(strict_types=1);
$file = 'counter.txt';
$data = '1';
$result = file_put_contents($file, $data, LOCK_EX);
if ($result !== false) {
echo "Wrote data with exclusive lock";
} else {
echo "Failed to acquire lock or write data";
}
LOCK_EX provides exclusive write access during the operation. This prevents race conditions in concurrent access scenarios. Always check the return value.
Combining Flags
You can combine multiple flags using the bitwise OR operator.
<?php
declare(strict_types=1);
$file = 'audit.log';
$data = "User action at " . date('Y-m-d H:i:s') . PHP_EOL;
$flags = FILE_APPEND | LOCK_EX;
$result = file_put_contents($file, $data, $flags);
if ($result !== false) {
echo "Appended with lock: $result bytes written";
} else {
echo "Failed to write with combined flags";
}
This combines FILE_APPEND and LOCK_EX for safe concurrent appending. The bitwise OR operator (|) combines the flags. Always test flag combinations thoroughly.
Best Practices
- Error Handling: Always check the return value.
- Permissions: Ensure proper file permissions.
- Validation: Sanitize input data before writing.
- Security: Avoid user-controlled filenames.
- Memory: For large data, consider streaming.
Source
PHP file_put_contents Documentation
This tutorial covered the PHP file_put_contents function with
practical examples showing its usage in different scenarios.