Improve validation and error messaging

[inghamn]

what are the possible errors?
What was the field?
Defer the message text to the view
Validation should throw a single exception

• Custom validation exception with errors added
• Errors in known data structure

$errors = [
    'fieldname' => [
        'errorType1', 'errorType2', 'errorType3
    ],
    'otherField' => [
        'otherFielderror', 'otherFieldProblem'
    ]
];

Model should define the validation fields and possible errors.
Model should implement the validation check

• Throw the exception
• Pack all the errors into the exception

Controller tries to save, catches the exception,
Passes the exception to the SESSION, and lets the form render

Model save triggers validation

$_SESSION['messages']['validation'] = $errors;