The error message

The exception classes that inherit from axy\errors\* are able to define the default message. Not to write it every time.

class MyError extends \axy\errors\Logic implements Error
{
    protected $defaultMessage = 'This is default message';
}

throw new MyError(); // This is default message
throw new MyError('message'); // message

The message template

In $defaultMessage can write a message template in which the variables are inserted using {{ var }}. Then, instead of a string you can pass an array of variables.

class QueryError extends \axy\errors\Logic
{
    protected $defaultMessage = 'Error #{{ code }} in query "{{ query }}": {{ error }}';

    public function __construct($query, $error, $code)
    {
        $this->query = $query;
        $this->error = $error;
        $message = [
            'query' => $query,
            'error' => $error,
        ];
        parent::__construct($message, $code);
    }

    final public function getQuery()
    {
        return $this->query;
    }

    final public function getError()
    {
        return $this->error;
    }

    private $query, $error;
}

Use:

class MyDB
{
    public function query($sql) 
    {
        if (!$this->db->query($sql)) {
            throw new QueryError($sql, $this->db->error, $this->db->errno);
        }
    }
}

Do a query to a nonexistent table:

$mydb->query('SELECT * FROM `unknown`');

Output:

QueryError: Error #1146 in query "SELECT * FROM `unknown`": Table 'test.unknown' doesn't exist

If one of the variables is an object then it can be reduced to a string. If it is impossible then reduced to empty string.

If {{ code }} is specified in the template and it is not found in an array used $code of the exception.