cep.php

<?php

function cep_dados($cep)
{
	$ch = curl_init();

	curl_setopt($ch, CURLOPT_URL, 'http://www.buscacep.correios.com.br/servicos/dnec/consultaLogradouroAction.do');
	curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
	curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
	curl_setopt($ch, CURLOPT_POST, true);
	curl_setopt($ch, CURLOPT_POSTFIELDS, 'CEP=' . $cep . '&Metodo=listaLogradouro&TipoConsulta=cep&StartRow=1&EndRow=10');
	curl_setopt($ch, CURLOPT_TIMEOUT, 60);

	$res = curl_exec($ch);
	curl_close($ch);

	if (strpos($res, 'CEP NAO ENCONTRADO') !== false)
	{
		return false;
	}

	$tabelas = explode('<table', $res);
	$tabela = '';

	foreach ($tabelas as $tbl)
	{
		if (strpos($tbl, 'javascript:detalharCep') !== false)
		{
			$tabela = $tbl;
			break;
		}
	}

	$tr = explode('<tr', $tabela);
	preg_match_all('/\<td[^>]+\>(.*?)\<\/td\>/', $tr[1], $tds);

	return array(
		'logradouro' => $tds[1][0],
		'bairro' => $tds[1][1],
		'cidade' => $tds[1][2],
		'estado' => $tds[1][3]
	);
}

var_dump(cep_dados('13537000'));