add new field in magento(1.9) customer registration without changing core files

Question

I am new in Magento development and customization I am trying to add a mobile field in new customers registration form I have followed this article but I am stuck https://stackoverflow.com/questions/11501020/magento-add-a-field-on-default-registration-form

So, Please guide me through the perfect way without changing core files.

Answer 1

<li>
    <label for="mobile" class="required"><em>*</em><?php echo $this->__('Mobile') ?></label> 
    <div class="input-box"> 
        <input type="text" name="mobile" id="mobile" value="<?php echo $this->htmlEscape($this->getFormData()->getMobile()) ?>" title="<?php echo $this->__('Mobile') ?>" class="input-text required-entry validate-phoneStrict validate-email" /> 
    </div> 
</li>

replace to

<li>
    <label for="mobile" class="required"><em>*</em><?php echo $this->__('Mobile') ?></label> 
    <div class="input-box"> 
        <input type="text" name="mobile" id="mobile" value="<?php echo $this->htmlEscape($this->getFormData()->getMobile()) ?>" title="<?php echo $this->__('Mobile') ?>" class="input-text required-entry validate-phoneStrict" /> 
    </div> 
</li>

You don't need validate-email if you need phone number validation