What potential issues or errors could arise when using the SQL query in the code?

One potential issue that could arise when using the SQL query in the code is SQL injection. To prevent this, you should use prepared statements with parameterized queries to sanitize user input and prevent malicious SQL queries from being executed. 

// Using prepared statements to prevent SQL injection
$connection = new mysqli("localhost", "username", "password", "database");

// Check connection
if ($connection->connect_error) {
    die("Connection failed: " . $connection->connect_error);
}

// Prepare the SQL query with a placeholder for the user input
$stmt = $connection->prepare("SELECT * FROM users WHERE username = ?");
$stmt->bind_param("s", $username);

// Set the user input and execute the query
$username = $_POST['username'];
$stmt->execute();

// Get the results
$result = $stmt->get_result();

// Fetch the data
while ($row = $result->fetch_assoc()) {
    // Process the data
}

// Close the statement and connection
$stmt->close();
$connection->close();

Keywords

SQL injection syntax error database connection mysqli_query error handling

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