If you don’t wish to have a boolean cast (not that there’s anything wrong with that) you can easily make it a boolean like this:
$value = rand(0,1) == 1;
Basically, if the random value is 1, yield true, otherwise false. Of course, a value of 0 or 1 already acts as a boolean value; so this:
if (rand(0, 1)) { ... }
Is a perfectly valid condition and will work as expected.
Alternatively, you can use mt_rand() for the random number generation (it’s an improvement over rand()). You could even go as far as openssl_random_pseudo_bytes() with this code:
$value = ord(openssl_random_pseudo_bytes(1)) >= 0x80;
Update
In PHP 7.0 you will be able to use random_int(), which generates cryptographically secure pseudo-random integers:
$value = (bool)random_int(0, 1);