Asked  7 Months ago    Answers:  5   Viewed   33 times

Is there a ternary operator or the like in PHP that acts like ?? of C#?

?? in C# is clean and shorter, but in PHP you have to do something like:

// This is absolutely okay except that $_REQUEST['test'] is kind of redundant.
echo isset($_REQUEST['test'])? $_REQUEST['test'] : 'hi';

// This is perfect! Shorter and cleaner, but only in this situation.
echo null? : 'replacement if empty';

// This line gives error when $_REQUEST['test'] is NOT set.
echo $_REQUEST['test']?: 'hi';

 Answers

53

PHP 7 adds the null coalescing operator:

// Fetches the value of $_GET['user'] and returns 'nobody'
// if it does not exist.
$username = $_GET['user'] ?? 'nobody';
// This is equivalent to:
$username = isset($_GET['user']) ? $_GET['user'] : 'nobody';

You could also look at short way of writing PHP's ternary operator ?: (PHP >=5.3 only)

// Example usage for: Short Ternary Operator
$action = $_POST['action'] ?: 'default';

// The above is identical to
$action = $_POST['action'] ? $_POST['action'] : 'default';

And your comparison to C# is not fair. "in PHP you have to do something like" - In C# you will also have a runtime error if you try to access a non-existent array/dictionary item.

Wednesday, March 31, 2021
 
radmen
answered 7 Months ago
99

Update

JavaScript now supports the nullish coalescing operator (??). It returns its right-hand-side operand when its left-hand-side operand is null or undefined, and otherwise returns its left-hand-side operand.

Please check compatibility before using it.


The JavaScript equivalent of the C# null coalescing operator (??) is using a logical OR (||):

var whatIWant = someString || "Cookies!";

There are cases (clarified below) that the behaviour won't match that of C#, but this is the general, terse way of assigning default/alternative values in JavaScript.


Clarification

Regardless of the type of the first operand, if casting it to a Boolean results in false, the assignment will use the second operand. Beware of all the cases below:

alert(Boolean(null)); // false
alert(Boolean(undefined)); // false
alert(Boolean(0)); // false
alert(Boolean("")); // false
alert(Boolean("false")); // true -- gotcha! :)

This means:

var whatIWant = null || new ShinyObject(); // is a new shiny object
var whatIWant = undefined || "well defined"; // is "well defined"
var whatIWant = 0 || 42; // is 42
var whatIWant = "" || "a million bucks"; // is "a million bucks"
var whatIWant = "false" || "no way"; // is "false"
Tuesday, June 1, 2021
 
PandemoniumSyndicate
answered 5 Months ago
69

This is a proposed feature in TypeScript, under the legendary Issue #16

It won't be introduced into TypeScript until the ECMAScript spec for this feature is firm as there is a desire for the TypeScript implementation to follow that specification - so you'll get it early, but not massively early in this case.

It is referred to as any of the following:

  • Null Propagation Operator
  • Existential Operator
  • Null Coalesce Operator
Sunday, August 22, 2021
 
Craig
answered 2 Months ago
62

Answer to your first question: Yes.

Short answer to your second question: None, you should choose based on which is more readable.

Answer to your third question: if you expect the whole expression to run "in one shot" and therefore not be subject to concurrency issues, then no, the null-coalescing operator does not guarantee that as explained in the answer of this Stackoverflow question. In both your examples you would actually face the same concurrency challenges.

Long answer to your second question:

Looking in the Microsoft '??' doc, all is mentioned is the operator purpose and function:

The ?? operator is called the null-coalescing operator. It returns the left-hand operand if the operand is not null; otherwise it returns the right hand operand.

Hence, the null-coalescing operator makes you write cleaner code that would otherwise require you to write the operand in question twice (as in your 2nd example).

Usage of the null-coalescing operator is more related to utility than performance, as explained is the accepted answer of a similar Stackoverflow question. Indeed, both perform quite the same.

Interesting to notice, as part of the same answer, the null-coalescing operator seems to perform slightly faster, but the difference is so little that could be ignored.

Wednesday, September 1, 2021
 
Lorav
answered 2 Months ago
66

This happens as consequence of the assignment operator also returning the value:

The assignment operator (=) stores the value of its right-hand operand in the storage location, property, or indexer denoted by its left-hand operand and returns the value as its result.

The expression b = 12 not only assigns 12 to b, but also returns this value.

Thursday, September 23, 2021
 
Michael Yuwono
answered 4 Weeks ago
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