Deprecation rules

This document details the rules available in the Deprecation category.

Rule	Code
Explicit Nullable Param	explicit-nullable-param
No Underscore Class	no-underscore-class
No Void Reference Return	no-void-reference-return
Optional Parameter Before Required	optional-param-order

explicit-nullable-param

Detects parameters that are implicitly nullable and rely on a deprecated feature.

Such parameters are considered deprecated; an explicit nullable type hint is recommended.

Requirements

• PHP version: >= 8.4.0

Configuration

Option	Type	Default
enabled	boolean	true
level	string	"warning"

Examples

Correct code

<?php

function foo(?string $param) {}

function bar(null|string $param) {}

function baz(null|object $param = null) {}

Incorrect code

<?php

function foo(string $param = null) {}

function bar(string $param = NULL) {}

function baz(object $param = null) {}

no-underscore-class

Detects class, interface, trait, or enum declarations named _.

Such names are considered deprecated; a more descriptive identifier is recommended.

Requirements

• PHP version: >= 8.4.0

Configuration

Option	Type	Default
enabled	boolean	true
level	string	"warning"

Examples

Correct code

<?php

class MyService {}

Incorrect code

<?php

class _ {}

no-void-reference-return

Detects functions, methods, closures, arrow functions, and set property hooks that return by reference from a void function. Such functions are considered deprecated; returning by reference from a void function is deprecated since PHP 8.0.

Requirements

• PHP version: >= 8.2.0

Configuration

Option	Type	Default
enabled	boolean	true
level	string	"warning"

Examples

Correct code

<?php

function &foo(): string {
    // ...
}

Incorrect code

<?php

function &foo(): void {
    // ...
}

optional-param-order

            Detects optional parameters defined before required parameters in function-like declarations.

Such parameter order is considered deprecated; required parameters should precede optional parameters.

Requirements

• PHP version: >= 8.0.0

Configuration

Option	Type	Default
enabled	boolean	true
level	string	"warning"

Examples

Correct code

<?php

function foo(string $required, ?string $optional = null): void {}

Incorrect code

<?php

function foo(?string $optional = null, string $required): void {}