Disable certificate verification in PHP SoapClient

SoapClient takes a stream context in its parameters, which you can create yourself. That way you can control almost every aspect of the transport layer:

$context = stream_context_create([
    'ssl' => [
        // set some SSL/TLS specific options
        'verify_peer' => false,
        'verify_peer_name' => false,
        'allow_self_signed' => true
    ]
]);

$client  = new SoapClient(null, [
    'location' => 'https://...',
    'uri' => '...', 
    'stream_context' => $context
]);

Documentation:

• stream_context_create() ^Docs
• HTTP context options ^Docs
• SSL context options ^Docs

The accepted answer works but only in the non-WSDL mode. If you try to use this in the WSDL mode (i. e. you pass a WSDL file url as the first argument) you will face the fact that the stream context is ignored when downloading WSDL files. So if the WSDL file is also located on a server with broken certificate, it will fail, most likely throwing the message failed to load external entity. See more here and here.

As suggested, the simplest way around is to download the WSDL file manually and pass the local copy to the SoapClient. You can download it for example with file_get_contents using the very same stream context from the accepted answer.

Note that you will also have to do this when creating a SoapServer.

The correct list for PHP 5.6.8 is

'ssl' => array('verify_peer_name'=>false, 'allow_self_signed' => true),