riddle.md

<?php
$x = false or true;
// => true
var_export($x);
// => false

$y = false || true;
// => true
var_export($y);
// => true

Why?

<?php
$x = false or true;

// becomes...

($x = false) or true;

// so you're assigning `false` to `$x` then comparing `$x` to `true`, which evaluates as true.

But

<?php
$x = false || true;

// becomes...

$x = (false || true);

// so you're assigning the result of the expression to `$x`