bisection method error while checking loop with f(p)

function p = bisection(f,a,b)
if f(a)*f(b)>0 
    disp('Wrong choice bro')
else
    p = (a + b)/2;
    err = abs(f(p));
    while err > 1e-7
   if f(a)*f(p)<0 
       b = p;
   else
       a = p;          
   end
    p = (a + b)/2; 
   err = abs(f(p));
    end
end

The above Bisection method is not working with f(x)=x*tan(x)+1 using the interval [1,2].

>> f=@(x)x*tan(x)+1;
>> bisection(f,1,2)

not giving any output and entering into infinite loop