Help me understand this code

Question

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What is the PHP ? : operator called and what does it do?

$id = isset($_GET['id']) ? intval($_GET['id']) : 0;

Can someone help me understand the above code? I'm fairly new to php :) What up with ? and :?

I would appreciate it!

This is a duplicate, please see http://stackoverflow.com/questions/1080247/php-operator. — Andrew Hare, Jul 21 '09 at 12:15
it's a duplicate of many questions on here, docs are here: http://docs.php.net/manual/en/language.expressions.php — SilentGhost, Jul 21 '09 at 12:16

score 7 · Answer 1 · answered Jul 21 '09 at 12:14

7

This is a ternary operator. This basically says

if(isset($_GET['id']))
{
   $id = intval($_GET['id']);
}
else
{
   $id = 0;
}

answered Jul 21 '09 at 12:14

scheibk

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Thomas Owens · Answer 2 · 2009-07-21T12:25:13.847

2

That is a ternary operator.

What is says that is if $_GET['id'] is set, $id is intval($_GET['id']), otherwise, $id is 0.

edited Jul 21 '09 at 12:25

answered Jul 21 '09 at 12:14

Thomas Owens

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It’s *a* ternary operator, not “the”. – Gumbo Jul 21 '09 at 12:16
As Jon Skeet says: 'It's not **the** ternary operator, but **a** ternary operator.' – alex Jul 21 '09 at 12:16
@Gumbo - stole the words out of my mouth! – alex Jul 21 '09 at 12:17
I think that should make it all bette. – Thomas Owens Jul 21 '09 at 12:25

score 1 · Answer 3 · answered Jul 21 '09 at 12:14

1

The ? and : are parts of an inline if.

Basically, if isset($_GET['id']) is true, intval($_GET['id']) is used. Otherwise, $id gets 0.

answered Jul 21 '09 at 12:14

Daniel A. White

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`if` is a statement but `?:` is an operator. That’s a difference! – Gumbo Jul 21 '09 at 12:19

score 1 · Answer 4 · answered Jul 21 '09 at 12:14

1

x ? y : z = if x is true then y else z

answered Jul 21 '09 at 12:14

Finer Recliner

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score 1 · Answer 5 · answered Jul 21 '09 at 12:16

1

That’s the conditional operator :

The expression (expr1) ? (expr2) : (expr3) evaluates to expr2 if expr1 evaluates to TRUE, and expr3 if expr1 evaluates to FALSE.

answered Jul 21 '09 at 12:16

Gumbo

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score 1 · Answer 6 · answered Jul 21 '09 at 12:16

1

It means exactly this:

$id = 0;
if(isset($_GET['id'])) {
    $id = intval($_GET['id'];
}

answered Jul 21 '09 at 12:16

karim79

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score 0 · Answer 7 · answered Jul 21 '09 at 12:13

0

This is short notation for an if. The notation is taken from C.

It could be re-written:

if (isset($_GET['id']) ) {
     $id = intval($_GET['id']);
} else {
     $id = 0;
}

answered Jul 21 '09 at 12:13

acrosman

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score 0 · Answer 8 · answered Jul 21 '09 at 12:14

0

Its called a ternary

it populates $id with intval($_GET['id']) if isset($_GET['id']) returns true else it will populate it with 0

answered Jul 21 '09 at 12:14

AutomatedTester

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score 0 · Answer 9 · edited Nov 13 '11 at 16:51

0

see: http://www.lizjamieson.co.uk/2007/08/20/short-if-statement-in-php/ and http://php.net/operators.comparison

edited Nov 13 '11 at 16:51

Mat

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answered Jul 21 '09 at 12:14

b0x0rz

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score 0 · Answer 10 · answered Jul 21 '09 at 12:15

0

If $_GET['id'] exists it sets $id = $_GET['id'], if not it sets $id = 0, it uses ternary. http://uk3.php.net/ternary

answered Jul 21 '09 at 12:15

TWA · Answer 11 · 2009-07-21T12:23:57.870

0

This is just shorthand for an if statement (ternary operator) and is the same as:

if (isset($_GET['id']))
{
    $id = intval($_GET['id']);
}
else
{
    $id = 0;
}

edited Jul 21 '09 at 12:23

answered Jul 21 '09 at 12:15

TWA

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score 0 · Answer 12 · answered Jul 21 '09 at 12:16

That's a ternary operator. Basically, it has a

if (condition) {

} else {

}

in one line.

The code says

If the GET var id has been set, then set the $id var to equal the integer of the GET's variable.

For arguments sake too, casting with (int) has been proven to be much faster.

score 0 · Answer 13 · answered Jul 21 '09 at 12:18

That statement essentially means this:

$id = 0;

if (isset($_GET['id']))
{
    $id = intval($_GET['id']);
}
else
{
    $id = 0;
}

The ?: operator means "if condition then result else other_result," all in one line. You're basically setting the value of the $id variable based on a boolean (true/false) condition. If the condition is true, the first result is used to set the value of the $id variable. Otherwise, it uses the second value.

Help me understand this code

13 Answers13