php - Comparison of 0 to a string fails -

update: 0 isn't using default value, after testing condition failing suggested answers.

function test($value='a') {    if ($value != 'a') {      echo 'ok';    }    else {      echo 'not ok';    } }  test(); // outputs not ok test('a'); // outputs not ok test(0); // outputs not ok, should output ok? test('0'); // outputs ok test(null); // outputs ok test(false); // outputs ok 

this kind of throwing 1 of functions. surprised see 0 , null works fine. know why php interpreting 0 default value?

in php, comparing string 'a' number 0 causes change of string number. in case 'a' gets converted 0, of course 0 == 0.

see here details.

for completeness, fix, same linked documentation is

use strict comparison operators (===, !==) comparison operators