What best practices should be followed when storing and retrieving data from text files in PHP, as shown in the code snippet provided?

When storing and retrieving data from text files in PHP, it is important to follow best practices to ensure data integrity and security. One common best practice is to properly sanitize and validate input data before writing it to a text file to prevent potential security vulnerabilities. Additionally, it is recommended to use file locking mechanisms when writing to a file to prevent race conditions and data corruption. When retrieving data from a text file, it is important to validate and sanitize the data before using it in your application to prevent security risks such as SQL injection or cross-site scripting attacks.

// Writing data to a text file
$data = "Hello, World!";
$filename = "data.txt";

$fp = fopen($filename, "a");
if (flock($fp, LOCK_EX)) {
    fwrite($fp, $data . PHP_EOL);
    flock($fp, LOCK_UN);
} else {
    echo "Could not lock the file!";
}
fclose($fp);

// Reading data from a text file
$lines = file($filename, FILE_IGNORE_NEW_LINES);
foreach ($lines as $line) {
    // Process each line of data
    echo $line . "<br>";
}