I just encountered the same errors. It’s an issue with older versions of PHP. In my case it’s GoDaddy’s Managed WordPress. They use an ancient version of PHP where several functions, including array_keys(), won’t accept function return values as parameters.
The solution that worked for me was assigning the function return value to a variable and using that as a parameter on class.mesh-templates.php.
I replaced lines 115 and 116 with this:
$mesh_post_types_array = get_option( ‘mesh_post_types’ );
$mesh_post_types = array_keys( $mesh_post_types_array );
$available_post_types = array_merge( array( ‘mesh_template’ ), $mesh_post_types );
@aware Would you mind changing that bit during your next update? So far as I can tell, it’s otherwise working in PHP Version 5.4.45. Thanks!