PHP operator difference && and "and" [duplicate]

Question

Possible Duplicate:
'AND' vs '&&' as operator

Sorry for very basic question but I started learning PHP just a week ago & couldn't find an answer to this question on google/stackoverflow.

I went through below program:

$one = true;
$two = null;
$a = isset($one) && isset($two);
$b = isset($one) and isset($two);

echo $a.'<br>';
echo $b;

Its output is:

false
true

I read &&/and are same. How is the result different for both of them? Can someone tell the real reason please?

Answer 1

The reason is operator precedence. Among three operators you used &&, and & =, precedence order is

• &&
• =
• and

So $a in your program calculated as expected but for $b, statement $b = isset($one) was calculated first, giving unexpected result. It can be fixed as follow.

$b = (isset($one) and isset($two));

Answer 2

Thats how the grouping of operator takes place

$one = true;
$two = null;
$a = (isset($one) && isset($two));
($b = isset($one)) and isset($two);

echo $a.'<br>';
echo $b;

Thats why its returning false for first and true for second.