For this Wordpress site http://mattmansell.ca/New2016RHB/ Error I got is "Warning: call_user_func_array() expects parameter 1 to be a valid callback, function 'vantage_chid_widgets_init' not found or invalid function name in /home/mattmans/public_html/R2/wp-includes/plugin.php on line 525" I got this after moving from MAMP to Server. Any ideas on how to tackle this?
If you are using short open tags, check that you have this turned on in your php.ini on your server.
However, this is considered bad practice, and recommended to only those who like to target practice with shooting themselves in the foot.
I was getting the same error as you, but when I checked my functions.php, the functions where there, in broad daylight, and even spelled correctly, and it through me off on a tangent.
There was a short
<? open tag in my functions.php, and this never failed because I had
short_open_tag = On
on my Mac's php.ini. When coming to deploy on Ubuntu server, things went horribly wrong, as this setting was off.