| 1 | <?php  | 
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| 14 | class HtmlIconGroups extends HtmlSemCollection { | 
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| 15 | |||
| 16 | 	public function __construct($identifier, $icons=array(), $size="") { | 
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| 21 | |||
| 22 | 	protected function createItem($value) { | 
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| 34 | |||
| 35 | 	protected function createCondition($value) { | 
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| 38 | |||
| 39 | 	public function getIcon($index) { | 
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| 42 | |||
| 43 | 	public function toCorner($index=1) { | 
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| 47 | }  | 
            
Let’s take a look at an example:
In the above example, the authenticate() method works fine as long as you just pass instances of MyUser. However, if you now also want to pass a different sub-classes of User which does not have a getDisplayName() method, the code will break.
Available Fixes
Change the type-hint for the parameter:
Add an additional type-check:
Add the method to the parent class: