Functions: Updated the getSalt() function so that it uses the mt_rand() function

Suggested implementation: getSalt3

Implementations:

/**
 * Original getSalt() in Gibbons
 */
function getSalt1() {
    $c = explode(' ', '. / a A b B c C d D e E f F g G h H i I j J k K l L m M n N o O p P q Q r R s S t T u U v V w W x X y Y z Z 0 1 2 3 4 5 6 7 8 9');
    $ks = array_rand($c, 22);
    $s = '';
    foreach ($ks as $k) {
        $s .= $c[$k];
    }
    return $s;
}

/**
 * A fixed version of the proposed getSalt() implementation in this PR.
 */
function getSalt2() {
    $c = explode(' ', '. / a A b B c C d D e E f F g G h H i I j J k K l L m M n N o O p P q Q r R s S t T u U v V w W x X y Y z Z 0 1 2 3 4 5 6 7 8 9');
    $ks = [];
    for ($x = 0; $x < 22; $x++) {
        $ind =  mt_rand(0, count($c) - 1);
        $ks[] = $c[$ind];
    }
    $s = '';
    foreach ($ks as $k) {
        $s .= $k;
    }
    return $s;
}

/**
 * A simplified version of getSalt2() provides better performance.
 */
function getSalt3() {
    $c = './aAbBcCdDeEfFgGhHiIjJkKlLmMnNoOpPqQrRsStTuUvVwWxXyYzZ0123456789';
    $s = '';
    $l = strlen($c);
    for ($x = 0; $x < 22; $x++) {
        $ind =  mt_rand(0, $l - 1);
        $s .= $c[$ind];
    }
    return $s;
}

Benchmark:

// Benchmarking the callback
function bench(string $name, Callable $cb, int $scale) {
    $start = microtime(true);
    echo "Benchmarking: $name\n";
    for ($i=0; $i<$scale; $i++) {
        $cb();
    }
    echo "time used: " .  sprintf("%.5f", (microtime(true) - $start)) . "s\n\n";
}

$scale = 500000;
bench('getSalt1()', getSalt1(...), $scale);
bench('getSalt2()', getSalt2(...), $scale);
bench('getSalt3()', getSalt3(...), $scale);

Results:

Benchmarking: getSalt1()
time used: 0.82821s

Benchmarking: getSalt2()
time used: 0.96580s

Benchmarking: getSalt3()
time used: 0.53052s

Outputs comparison (each run for 10 times):

getSalt1(): AbCeEGhHIlLMNPQtxXz012
getSalt1(): ./aABcDFghIKosuVwWx239
getSalt1(): BdDFgiJPqQRtUwxyYz2358
getSalt1(): /abcEfiIKlmMPQtTXyY036
getSalt1(): /bFgGjJlmMQUvVwWy12569
getSalt1(): ABeEFgHIjlLoPrRTUx0236
getSalt1(): .bBEfFHjkLPrvVxXYZ2569
getSalt1(): BcDEhHiImNPqruwyY06789
getSalt1(): aCdfFhikKMorRTuwWyz156
getSalt1(): aCDghIjmnoORstuvWx0246

getSalt2(): jUBTOqWBViKeKAICMJjnD7
getSalt2(): pu6JqHv6RBZc.0GLy8Zbcf
getSalt2(): G6clQF3bNLpm0VMZ98CqF4
getSalt2(): tQU2q0Iwfp4i5PqxNtWgP8
getSalt2(): 9sagx5Hd6mC5sSxaBz5cZD
getSalt2(): Ehi5qhDHj8DQHlr4EnqzGM
getSalt2(): kUNrIeKIsxNhmUeOlad24S
getSalt2(): zFHIHbijWiYZC/nc23wS58
getSalt2(): iS9DzCHFMqsu18XW8SToML
getSalt2(): OKUiCvQrdIw2haADebR4oC

getSalt3(): ZuTa0eEJ/.MNYOZSb4szp/
getSalt3(): .MuFfRUGZDiAbv8X.6NpKR
getSalt3(): 3EfMbZKpYHFBVWTIcL6i.X
getSalt3(): jlMZkbOSxUHwqa3IGm3bMI
getSalt3(): XnK3xuVCnVfI2iUj35Crlw
getSalt3(): 6YFV1cWXQCJW7ScQls/XUP
getSalt3(): wwlI8t.ljRLLT6KAsp3mZx
getSalt3(): AW6ctsr.NR/5BQfwTcgjTz
getSalt3(): bBvQLHegIok/lLLZfXOeQ.
getSalt3(): ERbKmyZqMkNDbwvuKAosWB

GibbonEdu / core

Functions: Updated the getSalt() function so that it uses the mt_rand() function #1798