如何在PHP自定义mysqli函数中显示SQL错误？

Question

I have found a PHP custom function for mysqli query functions, but my problem is, how can I show an error of the mysqli function?

Here is the sample php mysqli function:

function connect()
{
    $con    =   mysqli_connect(DB_HOST, DB_USER, DB_PASS);
    $db     =   mysqli_select_db($con, DB_NAME);
    return $con;
}

Query Function:

function query($sql)
{
    return mysqli_query(connect(),$sql);
}

Fetch Assoc Function:

function fetchAssoc($sql)
{
    return mysqli_fetch_assoc($sql);
}

And here is how it was called or used:

$sql_select = query("SELECT * FROM table_name");
$sql_result = fetchAssoc($sql_select);
$tbl_id = $sql_result['id'];

How can I show here if the SQL query is correct or have query error like incorrect field name or table does not exist?

Answer 1

After any query the last mysqli error is stored in the connection resourece. To retrieve it:

echo mysqli_error($con);

If you want to kill the script directly after the query if there is an error:

mysqli_query($con, "some query") or die(mysqli_error($con));

There is also error number if you ever have the need:

echo mysqli_errno($con);

Example:

mysqli_select_db($con, "something") or die(mysqli_error($con));
//if the database is not found it'd print out 'Unknown database "something"'