Difference between & and && in PHP

I am confused with & and &&. I have two PHP books. One says that they are same, but the another says they are different. I thought they are same as well.

Aren't they same?

Answer

& is bitwise AND. See Bitwise Operators. Assuming you do 14 & 7:

    14 = 1110
     7 = 0111
    ---------

14 & 7 = 0110 = 6

&& is logical AND. See Logical Operators. Consider this truth table:

 $a     $b     $a && $b
false  false    false
false  true     false
true   false    false
true   true     true