Unable to connect to Magento SOAP API v2 due to "failed to load external entity"

Question

I am unable to connect to the Magento SOAP API v2 using PHP. The error that occurs is:

PHP Fatal error: Uncaught SoapFault exception: [WSDL] SOAP-ERROR: Parsing WSDL: Couldn't load from 'http://www.example.com/index.php/api/v2_soap/index/wsdl/1/' : failed to load external entity "http://www.example.com/index.php/api/v2_soap/index/wsdl/1/"

As it seems, the WSDL is being loaded, but the external SOAP file which it includes not.

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PHP connection code:

$client = new SoapClient('http://www.example.com/api/v2_soap?wsdl=1');
$session = $client->login('username', 'password');

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Snip from v2_soap?wsdl=1 file:

<service name="MagentoService">
    <port name="Mage_Api_Model_Server_V2_HandlerPort" binding="typens:Mage_Api_Model_Server_V2_HandlerBinding">
        <soap:address location="http://www.example.com/index.php/api/v2_soap/index/"/>
    </port>
</service>

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Magento version is 1.5.1.0.

Answer 1

This problem is caused by the server not being able to access the file from the local machine. So the possible cause could've been the DNS server or /etc/hosts, but it was actually a .htaccess file blocking any hosts except from our development computers. This resulted in a 403 Forbidden error, which resulted in the SOAP error and so on..