Zend_Auth :: getInstance () will return an instance so that you can use it on any controller where you need it, make a shure to save data on a successful login, so that you do not need a model for authentication or testing if the user is authenticated. (with auth in your model it will load unnecessary clusters of the model in memory at the moments when they do not need you ..., the test, if the user is authenticated, must be placed in bootstrap)
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