foo.php

<?php

$data1 = [ "bla" => "foo", "whee" => [ "something", [ 1, 2, 3, 4, 5 ] ] ];
$data2 = [ "baz" => $data1, "heh" => $data1, "yep" => [6, 7, 8, 9 ,10 ] ];
$data3 = [ $data1, $data2, $data1, $data2, $data1, $data2 ];
$data4 = [ "something" => $data3, "else" => [$data1, $data2], "heh" => [ $data3, $data3, $data3 ] ];

define('COUNT', 100000);

timeIt("serialize/unserialize", function () use ($data4) {
    for ($i=0; $i<COUNT; $i++) {
        $ser = serialize($data4);
        $cmp = unserialize($ser);
        //if ($cmp !== $data4) {
        //    echo "Bad data!";
        //}
    }
});

timeIt("json_encode/json_decode", function () use ($data4) {
    for ($i=0; $i<COUNT; $i++) {
        $ser = json_encode($data4);
        $cmp = json_decode($ser, true);
        //if ($cmp !== $data4) {
        //    echo "Bad data!";
        //}
    }
});

function timeIt($label, $callback)
{
    $t1 = microtime(true);
    $callback();
    $t2 = microtime(true);

    echo "$label: " . ($t2-$t1) . " seconds\n";
}