Just one gotcha I wanted to mention about this. Grep will not match across multiple lines. Something like this would get completely missed by grepf:
function
ILikeToUseReturnALot ( $variable
$variable2
)
{
}

Also, for things that grepf does match, you may want to include -A 2 -B 2 along with the other parameters for grep. It will give you the two lines above and below the matching line which may contain comments or other parameters not included on the matching line which could give additional contextual help.