Help in retrieving all entities

Hi

I am trying to retrieve all the entities and getting error. Need help in integrating microsoft dynamic crm in php.

Below is my code. Please help me correcting it.

$xml = " <s:Body>";
$xml .= " <execute xmlns:i=\"www.w3.org/.../XMLSchema-instance\" xmlns=\"schemas.microsoft.com/.../Services\">";
$xml .= " <request i:type=\"a:RetrieveAllEntitiesRequest\" xmlns:a=\"schemas.microsoft.com/.../Contracts\">";
$xml .= " <a:parameters xmlns:b=\"schemas.datacontract.org/.../System.Collections.Generic\">";
$xml .= " <a:keyvaluepairofstringanytype>";
$xml .= " <b:key>EntityFilters</b:key>";
$xml .= " <b:value i:type=\"c:EntityFilters\" xmlns:c=\"schemas.microsoft.com/.../Metadata\">Entity</b:value>";
$xml .= " </a:keyvaluepairofstringanytype>";
$xml .= " <a:keyvaluepairofstringanytype>";
$xml .= " <b:key>RetrieveAsIfPublished</b:key>";
$xml .= " <b:value i:type=\"c:boolean\" xmlns:c=\"schemas.microsoft.com/.../Arrays\">true</b:value>";
$xml .= " </a:keyvaluepairofstringanytype>";
$xml .= " </a:parameters>";
$xml .= " <a:requestid i:nil=\"true\">";
$xml .= " <a:requestname>RetrieveAllEntities</a:requestname>";
$xml .= " </a:requestid>";
$xml .= " </request>";
$xml .= " </execute>";

$xml .= " </s:Body>";

$executeSoap = new CrmExecuteSoap ();
$response = $executeSoap->ExecuteSOAPRequest ( $authHeader, $xml, $url );

$responsedom = new DomDocument ();
$responsedom->loadXML ( $response );

echo "<pre>";
print_r($responsedom);
echo "</pre>";

this is the error I am getting

[textContent] => schemas.microsoft.com/.../faulturn:uuid:{530CEDCF-4076-4CF5-E81B-674B85807CD1}00000000-0000-0000-0000-0000000000002015-11-03T06:56:11.208Z2015-11-03T07:01:11.208Zs:Receivera:InternalServiceFaultThe server was unable to process the request due to an internal error.  For more information about the error, either turn on IncludeExceptionDetailInFaults (either from ServiceBehaviorAttribute or from the  configuration behavior) on the server in order to send the exception information back to the client, or turn on tracing as per the Microsoft .NET Framework SDK documentation and inspect the server trace logs.