Leer xml php

[leo_nqn]

Creo que hay algo que no dije.. necesito ese dato en la hoja php que les mostre.. osea donde lo recibo quiero obtener el dato.
Agregue esto al codigo de ipn_dineromail.php:

header ('Content-type: text/xml');

$xml1 = simplexml_load_string($content);
foreach ($xml1->ESTADO as $dato1) {
echo $dato1->ESTADO;
}

y tira este error:

Warning: Cannot modify header information - headers already sent by (output started at /usr/local/pem/vhosts/109127/webspace/httpdocs/ipn_dineromail.php:52) in /usr/local/pem/vhosts/109127/webspace/httpdocs/ipn_dineromail.php on line 53 Warning: simplexml_load_string(): Entity: line 1: parser error : Start tag expected, '<' not found in /usr/local/pem/vhosts/109127/webspace/httpdocs/ipn_dineromail.php on line 55 Warning: simplexml_load_string(): 497 in /usr/local/pem/vhosts/109127/webspace/httpdocs/ipn_dineromail.php on line 55