Something simple and functional is to use timestamp information
$token = microtime();
Something like this will come back
0.13287600 1460718460
If you do not want the space character you can generate as well:
$token = microtime(true);
Will return something like: 1460718491.9867
Of course, if this uuid/token is publicly accessible, it is recommended to encrypt it at least to prevent anyone from understanding how the token is generated. In this example, using timestamp any programmer can guess that the format is a timestamp and with that can make a token hijacking. So if you use a very obvious sequence, encrypt it.
$token = hash('sha256', microtime(true));
//gera algo como `6d20018cf7023becaf77a2e0dc5d4034894aebdde9febb093f83dbcc3744bce0`
coincidence.. is almost related to this: http://answall.com/questions/80604/qual%C3%A9-a-l%C3%B3gica-de-um-carrinho-de-compras-de-compras
– Daniel Omine