What potential issue is identified in the PHP code related to checking if a file is in the database?

The potential issue in the PHP code related to checking if a file is in the database is that it is vulnerable to SQL injection attacks. The code directly concatenates user input into the SQL query without sanitizing it, making it possible for malicious users to manipulate the query. To solve this issue, it is recommended to use prepared statements with parameterized queries to prevent SQL injection attacks.

// Potential issue - vulnerable to SQL injection
$filename = $_GET['filename'];
$query = "SELECT * FROM files WHERE filename = '$filename'";
$result = mysqli_query($connection, $query);

// Fix using prepared statement
$filename = $_GET['filename'];
$query = "SELECT * FROM files WHERE filename = ?";
$stmt = mysqli_prepare($connection, $query);
mysqli_stmt_bind_param($stmt, "s", $filename);
mysqli_stmt_execute($stmt);
$result = mysqli_stmt_get_result($stmt);