cakePHP value for empty option

Using the verbose array syntax you can chose any value for empty:

echo $this->Form->input('supplier_id', ['empty' => ['0' => '']]);

See http://www.dereuromark.de/2010/06/23/working-with-forms/

echo $this->Form->input('supplier_id', array('empty'=>'Select'));

You can also add required to it:

echo $this->Form->input('supplier_id', array('empty'=>'Select', 'required' => true));