Whats is the best way to generate uuidv4 in php?

Whats is the best way to generate uuidv4 in php?
Some people use this: https://github.com/ramsey/uuid
Others can user a system call like file_get_contents('/proc/sys/kernel/random/uuid');
And others just a simple function.

What's the best way? Depending on your needs, of course.
I can use all the option, so I decide to make a benchmark, and I was surprised...

<?php
require __DIR__.'/../vendor/autoload.php';
function gen_uuidv4(){
    return sprintf('%04x%04x-%04x-%04x-%04x-%04x%04x%04x',
            // 32 bits for "time_low"
            mt_rand(0,0xffff),mt_rand(0,0xffff),
            // 16 bits for "time_mid"
            mt_rand(0,0xffff),
            // 16 bits for "time_hi_and_version",
            // four most significant bits holds version number 4
            mt_rand(0,0x0fff)|0x4000,
            // 16 bits, 8 bits for "clk_seq_hi_res",
            // 8 bits for "clk_seq_low",
            // two most significant bits holds zero and one for variant DCE1.1
            mt_rand(0,0x3fff)|0x8000,
            // 48 bits for "node"
            mt_rand(0,0xffff),mt_rand(0,0xffff),mt_rand(0,0xffff));
}
// #####################################
$i=microtime(true);
for($a=0;$a<1000000;$a++){
    file_get_contents('/proc/sys/kernel/random/uuid');
}
$f=microtime(true);
$t1=$f-$i;
echo $t1;
echo '<br>';
// #####################################
$i=microtime(true);
for($a=0;$a<1000000;$a++){
    gen_uuidv4(true);
}
$f=microtime(true);
$t2=$f-$i;
echo $t2;
echo '<br>';
// #####################################
$i=microtime(true);
for($a=0;$a<1000000;$a++){
    \Ramsey\Uuid\Uuid::uuid4();
}
$f=microtime(true);
$t3=$f-$i;
echo $t3;


T1: 10.762820005417(s) System Call in Ubuntu 14.04
T2: 6.3450520038605(s) simple function
T3: 30.962769985199(s) blotted library

Choose wisely :)