Question

php, my dearest old frienemy.

ok, so i can come to terms with why the string ‘0’ would be a falsie value. that’s only fair seeing as how '0' is the same as 0 in a loosely typed language, and 0 is false in a loosely typed language. so this gives that false == 0 == '0'.

fine fine… BUT!! what is this all about?

<?php
    print "number of surprised persons: " . ('false' == 0);

the output is….

number of surprised persons: 1

how is this reasonable? am i the only one who’s surprised by this? what am i failing to see?

further testing has proven that the integer 0 is equal (by operator ==) to

0        <-- integer
false    <-- boolean
null     <-- just.. you know, null
'0'      <-- string
''       <-- string
'false'  <-- string
'true'   <-- string
'null'   <-- string

naturally, i mostly use operator === to compare stuff. and now that i know about this, i’ll have to adjust my programming of course, no question about that. but still! can someone shed some light pl0x?

Answer 1

It’s because, when you compare a string to an integer, they don’t both get converted to strings, or to booleans – they get converted to integers. For PHP, when you think about it, this isn’t strange at all (comparatively, I suppose).

'true' == 0
// is the same as
(int)'true' == 0
// is the same as
0 == 0
// is the same as
true

And this is true for any non-numeric string as well as the string "0". The reason 1 is printed out is because the string version of true is 1 (and the string version of false is an empty string).