Help with my first Metabox helper class

The problem seems on the line no 279 of metabox class api definition, below is your code:

'<img src="'.$label.'" class="optionimg '.$selected_value.'" onclick="document.getElementById(\
''.$field['id'].$choices.'\').checked=true" style="display:inline-block;" /><input type="radio" 
name="%s" id="%s" value="%s" style="display:none;"/>',

$choices is not defined variable in the scope (error thrown by WAMP), I think you should replace $field['id'].$choices with $value as in below code:

'<img src="'.$label.'" class="optionimg '.$selected_value.'" onclick="document.getElementById(\
''.$value.'\').checked=true" style="display:inline-block;" /><input type="radio"
name="%s" id="%s" value="%s" style="display:none;"/>',

Hope it helps.