PHP operators difference

Question

What is the difference between
I)or and ||
II)and and &&

If they are all same, why is there no symbol for xor operator?

Answer 1

no it is not the same.
the priority of && (higher than ||) and AND is different (lower than ||)
$a && $b || $c means ($a and $b) or $c
$a AND $b || $c means $a and ($b or $c)