Null Coalescing vs Elvis Operator in PHP

1. Elvis Operator in PHP
2. Null Coalescing Operator in PHP

This article will differentiate the null coalescing operator and the Elvis operator in PHP with demonstrations.

Elvis Operator in PHP

First, let’s know about the Elvis operator. PHP Elvis operator is a shorthand operator for the ternary operator.

We can also say that it is a modified form of the ternary operator. To understand the PHP Elvis operator, we must know the ternary operator and how it works.

A ternary operator is a conditional operator used to perform a simple comparison or check on a condition having simple statements. It is a shorter version of the if-else statement.

It decreases the length of code performing conditional operations. The order of the operation is from left to right.

Syntax:

condition? statement1 : statement2;

In the ternary operator, firstly, the condition is evaluated. If the condition is true, statement1 is executed, and if the condition is false, statement2 is executed.

It is called a ternary operator as it takes three operands, i.e., a condition, a result statement for true, and a statement for false.

Example Code:

<?php
$marks = 80;
$result = $marks >= 40 ? 'Pass': 'Fail';
echo $result;
?>

The above example will display Pass as the condition $marks >= 40 is true.

Output:

Pass

Now let’s have a look at the Elvis operator. It is slightly different from the ternary operator; it just leaves out the second operand (between condition and statement2) and makes it even shorter.

Syntax:

condition?:statement;

Here, if the condition evaluates to true, it returns condition. Else, it will return statement.

The ternary representation of the above Elvis syntax is shown below.

conditon ? condition : statement;

Note: Values like 0, false, NULL, "", [], "0", etc., are considered to be false values in PHP.

Let’s see some examples of Elvis operators.

Example Code:

<?php
$name = "John Doe";
$yourName = $name ?: 'No name';
echo $yourName."<br>";

$marks = "";
$yourMarks = $marks ?: 'No marks';
echo $yourMarks."<br>";

$address = null;
$yourAddress = $address ?: 'No Address';
echo $yourAddress."<br>";

$age = false;
$yourAge = $age ?: 'No age';
echo $yourAge."<br>";
?>

Output:

John Doe
No marks
No Address
No age

Since the $name variable returns true, the variable’s value is evaluated. In the rest of the cases, the variables $marks, $address, and $age return false, so the operands on the right-hand side are evaluated.

Thus, we can conclude that the output of the Elvis operator depends on the true or false state of the condition.

Null Coalescing Operator in PHP

The null coalescing operator checks whether the given variable is null or not, and it returns the non-null value from the pair of the values. The output of the null coalescing operator depends on whether the variable is null.

Let’s see the syntax below to understand it.

statment1 ?? statement2;

Here, if statment1 evaluates to be null, statment2 will be returned. If statment1 is a non-null value, it will be returned.

In the null coalescing operator, it does not matter if the value of statement is false, 0, or ''. Even if statement has falsy values, its value will be returned.

This is the main difference between the Elvis operator and the null coalescing operator. Some examples of the null coalescing operators are:

Example Code:

<?php
$name = "John Doe";
$yourName = $name ?? 'No name';
echo $yourName."<br>";

$marks = "";
$yourMarks = $marks ?? 'No marks';
echo $yourMarks."<br>";

$age = false;
$yourAge = $age ?? 'No age';
echo $yourAge."<br>";

$address = null;
$yourAddress = $address ?? 'No Address';
echo $yourAddress."<br>";
?>

Output:

John Doe


No Address

Here, the variable $name is true, then it is evaluated and printed in the output section. Next, the variable $marks is an empty string; an empty string is a falsy value.

The second operand is not evaluated since it is not a null value. There is a blank in the output section because the empty string is evaluated.

The case is the same for the $age variable as it holds a falsy value but not a null value. Finally, the $address variable has a null value; therefore, the second operand, No Address, is evaluated.

From the above examples and explanation, we can conclude the significant difference between the Elvis operator and the null coalescing operator is that the Elvis operator checks whether the value is true. Still, the null coalescing operator checks if the value is not null.