How can beginners troubleshoot and debug SQL queries in PHP when not receiving expected results?

One common way to troubleshoot and debug SQL queries in PHP is to echo or print out the SQL query before executing it. This allows you to see the actual query being sent to the database, which can help identify any syntax errors or unexpected values. Additionally, checking for error messages returned by the database can provide valuable information on why the query is not returning the expected results.

// Example SQL query
$sql = "SELECT * FROM users WHERE id = $user_id";

// Echo the SQL query for debugging
echo $sql;

// Execute the query
$result = mysqli_query($connection, $sql);

// Check for errors
if (!$result) {
    die('Error: ' . mysqli_error($connection));
}

// Process the query results
while ($row = mysqli_fetch_assoc($result)) {
    // Do something with the data
}

// Free the result set
mysqli_free_result($result);

// Close the database connection
mysqli_close($connection);