php - minlength doesn't work with jquery validation -

i using jquery validation in zend 2. other validation types working except minlength.
here form code:

    $this->add(array(         'name' => 'usr_name',          'attributes' => array(             'type'  => 'text',             'id' => 'firstname',             'class'  => 'form-control',          // jquery validation rules:             'required'  => 'true',             'minlength'  => '2',             'maxlength'  => '20',         ),         'options' => array(             'label' => 'name',         ),     )); 

here js code:

 $('.form-validation').each(function () {      $(this).validate({       errorelement: "span",     errorclass: "help-block",         highlight: function(element) {         $(element).closest('.control-group').removeclass('success').addclass('error');         $(element).attr('style', "border-radius: 5px; border:#ff0000 1px solid;");     },     unhighlight: function(element) {         $(element).addclass('valid').closest('.control-group').removeclass('error').addclass('success');         $(element).attr('style', "border-radius: 4px; border:1px solid #ccc;");     },     errorplacement: function (error, element) {         $(error).attr('style', "color: #ff0000;");         if ( element.prop('type') === 'checkbox') {             error.insertafter(element.parent());         } else {             error.insertafter(element);         }     }    });  }); 

update :
html generated:

<input name="usr_name" type="text" required="required" maxlength="20" id="firstname" class="form-control" value="" aria-required="true"> 

look @ this:

strange, how can possible!

i found following article.

which strange how zf2 people consider logic!!

so ugly workaround injected minlength attribute in needed elements in following way:

 $('.minlength').each(function () {      $(this).attr("minlength", "8");  }); 

where minlength class added optionally needed elements give jquery opportunity work on them properly!