To use the OR operator, you have to be comparing boolean values. Those values can be produced by a comparison, so
if ((/ comparison /) or (/ comparison /) or (/ comparison /))
{/ something /}
else
{/ something else /}
... would be proper. That may be different from the notation a human being would prefer, but PHP requires it.
A comparison must be simple:
($var == 'value')
So ...
if ((($var == 'value1') or (($var == 'value2')) or (($var == 'value3')))
{/ something /}
else
{/ something else /}