Difference between & and && in PHP

Solution 1:

& 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

Solution 2:

The other answers are correct, but incomplete. A key feature of logical AND is that it short-circuits, meaning the second operand is only evaluated if necessary. The PHP manual gives the following example to illustrate:

$a = (false && foo());

foo will never be called, since the result is known after evaluating false. On the other hand with

$a = (false & foo());

foo will be called (also, the result is 0 rather than false).