Fix posts discovery.

For PHP before 5.5, the bridge is not working. It returns the following error: "Can't use method return value in write context".
See the following message for explanations: http://stackoverflow.com/questions/1075534/cant-use-method-return-value-in-write-context/4328049#4328049
Merge pull request #53 from aledeg/wordpress

[WordpressBridge] Fix posts discovery for PHP 5.5-