Root index and login pages show php error

I've started getting this error:
Fatal error: Call to undefined function json_decode() in /var/www/html/omeka/plugins/HideElements/HideElementsPlugin.php on line 32

when I go to either the root directory or the login page for an Omeka instance.

Php appears to be working to judge from info.php page. Though we changed where it lives on the server and Omeka was working prior to the php changes.

Nothing is showing in the errors.log file.

Just trying to get some direction as to where this might have broken.

This is Omeka 2.0.4 on RHEL 6 with php 5.5


Bobb Menk
MIT Lincoln Laboratory

Looks like you're missing PHP's JSON support. That's almost always installed, but it looks like it isn't here.

Yup - that's it. Somehow it didn't make the transition when we moved php around.