Olá @Matheus Tavares, obrigado por sua resposta.
Eu dei o var_dump e ele me trás a seguinte estrutura:
Onde era data, alterei pra endDate.
object(SimpleXMLElement)[5]
public 'code' (length=16)
public 'vigency'
object(SimpleXMLElement)[6]
public 'endDate' (length=19)
public 'link' (length=40)
public 'discount' (length=2)
public 'store'
object(SimpleXMLElement)[7]
public 'name' (length=6)
public 'id' (length=4)
public 'image1' (length=58)
public 'title' (length=76)
public 'category'
object(SimpleXMLElement)[8]
public 'name' (length=18)
public 'id' (length=2)
Obrigado.
