Handle Null Values in PHP – A Comprehensive Guide

In PHP, null is a distinct data type representing a variable with no assigned value. Whether a variable is set to null explicitly or through the `settype()` function, it signifies the absence of a meaningful value.

This article explores various techniques to handle null values in PHP, offering a comprehensive guide for developers.

1. The `is_null()` Function

The `is_null()` function serves as a fundamental tool to check whether a variable is null or not. It returns `true` if the variable is null and `false` otherwise.

$foo = null;

if (is_null($foo)) {
echo '$foo is null';
}

// Output: $foo is null

Note that `is_null()` solely checks for null values and does not determine whether a variable is set. To verify if a variable is set, combine it with the `isset()` function.

2. The Null Coalescing Operator (??)

Introduced in PHP 7.0, the null coalescing operator (`??`) provides an elegant way to handle null values. It returns the value of the variable if it’s not null; otherwise, it returns the value of the second operand.

$foo = null;

echo $foo ?? 'bar';
// Output: bar

Chaining the null coalescing operator allows checking multiple variables in succession.

$foo = null;

echo $foo ?? $bar ?? 'baz';
// Output: baz

Be cautious, as the null coalescing operator will return the second operand even if the variable is not set or undefined.

echo $bar ?? 'foo';
// Output: foo

3. The Null Coalescing Assignment Operator (??=)

Introduced as part of PHP 7.4, the null coalescing assignment operator (`??=`) simplifies assigning a value to a variable only if it’s null.

$foo = null;

$foo ??= 'bar';

echo $foo;
// Output: bar

4. The Nullsafe Operator (?->)

Introduced in PHP 8.0, the nullsafe operator (`?->`) facilitates safe method/property calls on a variable. It returns the method value if the variable is not null and null otherwise.

class User
{
public function getName()
{
return 'John Doe';
}
}

$user = null;
echo $user?->getName();
// Output: null

$user = new User;
echo $user?->getName();
// Output: John Doe

5. The Ternary Operator

While not as recommended for readability, the ternary operator can still be used to check if a variable is null.

$foo = null;

echo $foo ? $foo : 'bar';
// Output: bar

6. Nullable Types

Since PHP 7.1, you can explicitly declare function parameters or return types as nullable using the `?` operator.

function foo(?string $bar): ?string
{
return $bar;
}

echo foo(null);
// Output: null

echo foo('bar');
// Output: bar

7. Null as a Standalone Type (PHP 8.2 onwards)

Starting from PHP 8.2, you can use `null` as a standalone type. This allows declaring variables or function return types explicitly as `null`.

class Nil
{
public null $nil = null;

public function isNull(null $nil): null
{
return null;
}
}

$nil = new Nil;

$nil->isNull(null);
// Returns: null

$nil->isNull('foo');
// Fatal error: Argument #1 ($nil) must be of type null, string given

Embracing these techniques equips developers with a versatile set of tools for handling null values in PHP, promoting cleaner, more readable code that gracefully manages variables without assigned values.