What is the difference between the | and || operators?

16
votes

| and || - what is the difference between these two operators in PHP?

5
phpoperators
PHP Language Reference : Operators – bdl
possible duplicate of What is the diffference between the | and || or operators? – outis

5 Answers

12
votes

Meaning

| is binary operator, it will binary OR the bits of both the lefthand and righthand values.

|| is a boolean operator, it will short circuit when it encounters 'true' (any non-zero value, this includes non-empty arrays).

Examples

print_r(1 | 2)  // 3
print_r(1 || 2) // 1

When used with functions:

function numberOf($val) {
    echo "$val, ";
    return $val;
}

echo numberOf(1) | numberOf(2);  // Will print 1, 2, 3
echo numberOf(1) || numberOf(2); // Will print 1, 1
1
votes

Just like the & and && operator, the double Operator is a "short-circuit" operator.

For example:

if(condition1 || condition2 || condition3) If condition1 is true, condition 2 and 3 will NOT be checked.

if(condition1 | condition2 | condition3) This will check conditions 2 and 3, even if 1 is already true. As your conditions can be quite expensive functions, you can get a good

performance boost by using them.

There is one big caveat, NullReferences or similar problems. For example:

if(class != null && class.someVar < 20) If class is null, the if-statement will stop after "class != null" is false. If you only use &, it will try to check class.someVar and you get a

nice NullReferenceException. With the Or-Operator that may not be that much of a trap as it's unlikely that you trigger something bad,

but it's something to keep in mind.

No one ever uses the single & or | operators though, unless you have a design where each condition is a function that HAS the be

executed. Sounds like a design smell, but sometimes (rarely) it's a clean way to do stuff. The & operator does "run these 3 functions,

and if one of them returns false, execute the else block", while the | does "only run the else block if none return false" - can be useful,

but as said, often it's a design smell.

0
votes

| operates on the bits of a variable: 2 | 4 = 6

|| operates on The Boolean value of a variable: 2 || 4 = TRUE

0
votes

| -> binary operator || -> Boolean operator or -> also a Boolean operator with lower precedence

$x = false | true; //will set $x to an integer
$x = false || true; //will set $x to true
$x = false or true; //will set $x to false exactly the same that:
($x = false) || true;