gistfile1.php

<?php

        $this->addElement(new Zend_Form_Element_Text('phone_number'));
        $this->getElement('phone_number')
             ->setLabel('Phone Number')
             ->setRequired(true)
             ->addValidator('StringLength',false, 10)
             ->addValidator('Regex',false, array('/^[+]?[-\d() .]*$/i', 'message'=>'Please provide a valid Phone Number.'))
             ->setErrorMessages(array(''))
             ;