chore: pass correct param names in request body for php (#628)

# Fixes #
In PHP, the JSON request body params were not resolved correctly. They
were to be read from `name` instead of `baseName` since baseName is
explicitly being converted to camelCase. Fixing this enable users to
access the JSON Payload APIs correctly.

src/main/resources/twilio-php/models/modelClass.mustache

@@ -10,7 +10,7 @@ class {{classname}} implements \JsonSerializable
     {{/vars}}
     public function __construct(array $payload = []) {
     {{#vars}}
-        $this->{{#lambda.camelcase}}{{baseName}}{{/lambda.camelcase}} = Values::array_get($payload, '{{#lambda.camelcase}}{{baseName}}{{/lambda.camelcase}}');
+        $this->{{#lambda.camelcase}}{{baseName}}{{/lambda.camelcase}} = Values::array_get($payload, '{{name}}');
     {{/vars}}
     }