Essential Books

Null Coalescing Operator

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Null coalescing is a new operator introduced in PHP 7. This operator returns its first operand if it is set and not NULL. Otherwise it will return its second operand.

The following example: 

$name = $_POST['name'] ?? 'nobody';

is equivalent to both: 

if (isset($_POST['name'])) {
    $name = $_POST['name'];
} else {
    $name = 'nobody';
}

and: 

$name = isset($_POST['name']) ? $_POST['name'] : 'nobody';

This operator can also be chained (with right-associative semantics): 

$name = $_GET['name'] ?? $_POST['name'] ?? 'nobody';

which is an equivalent to: 

if (isset($_GET['name'])) {
    $name = $_GET['name'];
} elseif (isset($_POST['name'])) {
    $name = $_POST['name'];
} else {
    $name = 'nobody';
}

Note: When using coalescing operator on string concatenation dont forget to use parentheses () 

$firstName = "John";
$lastName = "Doe";
echo $firstName ?? "Unknown" . " " . $lastName ?? "";

This will output John only, and if its $firstName is null and $lastName is Doe it will output Unknown Doe. In order to output John Doe, we must use parentheses like this. 

$firstName = "John";
$lastName = "Doe";
echo ($firstName ?? "Unknown") . " " . ($lastName ?? "");

This will output John Doe instead of John only.

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Operators:
* Operators
* Null Coalescing Operator
* Spaceship Operator
* Execution Operator
* Incrementing and Decrementing Operators --
* Ternary Operator
* Logical Operators AND and OR
* String Operators . and .
* Object and Class Operators
* Combined Assignment etc
* Altering operator precedence with parentheses
* Association
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* Comparison Operators
* Bitwise Operators
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