Cognitive Complexity

Cognitive Complexity is a measure of how difficult a unit of code is to intuitively understand. Unlike Cyclomatic Complexity, which determines how difficult your code will be to test, Cognitive Complexity tells you how difficult your code will be to read and comprehend.

A method's cognitive complexity is based on a few simple rules:

• Code is not considered more complex when it uses shorthand that the language provides for collapsing multiple statements into one
• Code is considered more complex for each "break in the linear flow of the code"
• Code is considered more complex when "flow breaking structures are nested"

Further reading

• Cognitive Complexity docs
• Cognitive Complexity: A new way of measuring understandability

CouplingBetweenObjects

Since: 1.1.0

A class with too many dependencies has negative impacts on several quality aspects of a class. This includes quality criteria like stability, maintainability and understandability

Example

class Foo {
    /**
     * @var \foo\bar\X
     */
    private $x = null;

    /**
     * @var \foo\bar\Y
     */
    private $y = null;

    /**
     * @var \foo\bar\Z
     */
    private $z = null;

    public function setFoo(\Foo $foo) {}
    public function setBar(\Bar $bar) {}
    public function setBaz(\Baz $baz) {}

    /**
     * @return \SplObjectStorage
     * @throws \OutOfRangeException
     * @throws \InvalidArgumentException
     * @throws \ErrorException
     */
    public function process(\Iterator $it) {}

    // ...
}

Source https://phpmd.org/rules/design.html#couplingbetweenobjects

CouplingBetweenObjects

Since: 1.1.0

A class with too many dependencies has negative impacts on several quality aspects of a class. This includes quality criteria like stability, maintainability and understandability

Example

class Foo {
    /**
     * @var \foo\bar\X
     */
    private $x = null;

    /**
     * @var \foo\bar\Y
     */
    private $y = null;

    /**
     * @var \foo\bar\Z
     */
    private $z = null;

    public function setFoo(\Foo $foo) {}
    public function setBar(\Bar $bar) {}
    public function setBaz(\Baz $baz) {}

    /**
     * @return \SplObjectStorage
     * @throws \OutOfRangeException
     * @throws \InvalidArgumentException
     * @throws \ErrorException
     */
    public function process(\Iterator $it) {}

    // ...
}

Source https://phpmd.org/rules/design.html#couplingbetweenobjects

MissingImport

Since: 2.7.0

Importing all external classes in a file through use statements makes them clearly visible.

Example

function make() {
    return new \stdClass();
}

Source http://phpmd.org/rules/cleancode.html#MissingImport

MissingImport

Since: 2.7.0

Importing all external classes in a file through use statements makes them clearly visible.

Example

function make() {
    return new \stdClass();
}

Source http://phpmd.org/rules/cleancode.html#MissingImport

Cognitive Complexity

Cognitive Complexity is a measure of how difficult a unit of code is to intuitively understand. Unlike Cyclomatic Complexity, which determines how difficult your code will be to test, Cognitive Complexity tells you how difficult your code will be to read and comprehend.

A method's cognitive complexity is based on a few simple rules:

• Code is not considered more complex when it uses shorthand that the language provides for collapsing multiple statements into one
• Code is considered more complex for each "break in the linear flow of the code"
• Code is considered more complex when "flow breaking structures are nested"

Further reading

• Cognitive Complexity docs
• Cognitive Complexity: A new way of measuring understandability

Cognitive Complexity

Cognitive Complexity is a measure of how difficult a unit of code is to intuitively understand. Unlike Cyclomatic Complexity, which determines how difficult your code will be to test, Cognitive Complexity tells you how difficult your code will be to read and comprehend.

A method's cognitive complexity is based on a few simple rules:

• Code is not considered more complex when it uses shorthand that the language provides for collapsing multiple statements into one
• Code is considered more complex for each "break in the linear flow of the code"
• Code is considered more complex when "flow breaking structures are nested"

Further reading

• Cognitive Complexity docs
• Cognitive Complexity: A new way of measuring understandability

UnusedLocalVariable

Since: 0.2

Detects when a local variable is declared and/or assigned, but not used.

Example

class Foo {
    public function doSomething()
    {
        $i = 5; // Unused
    }
}

Source https://phpmd.org/rules/unusedcode.html#unusedlocalvariable

IfStatementAssignment

Since: 2.7.0

Assignments in if clauses and the like are considered a code smell. Assignments in PHP return the right operand as their result. In many cases, this is an expected behavior, but can lead to many difficult to spot bugs, especially when the right operand could result in zero, null or an empty string and the like.

Example

class Foo
{
    public function bar($flag)
    {
        if ($foo = 'bar') { // possible typo
            // ...
        }
        if ($baz = 0) { // always false
            // ...
        }
    }
}

Source http://phpmd.org/rules/cleancode.html#ifstatementassignment

UnusedLocalVariable

Since: 0.2

Detects when a local variable is declared and/or assigned, but not used.

Example

class Foo {
    public function doSomething()
    {
        $i = 5; // Unused
    }
}

Source https://phpmd.org/rules/unusedcode.html#unusedlocalvariable

StaticAccess

Since: 1.4.0

Static access causes unexchangeable dependencies to other classes and leads to hard to test code. Avoid using static access at all costs and instead inject dependencies through the constructor. The only case when static access is acceptable is when used for factory methods.

Example

class Foo
{
    public function bar()
    {
        Bar::baz();
    }
}

Source https://phpmd.org/rules/cleancode.html#staticaccess

IfStatementAssignment

Since: 2.7.0

Assignments in if clauses and the like are considered a code smell. Assignments in PHP return the right operand as their result. In many cases, this is an expected behavior, but can lead to many difficult to spot bugs, especially when the right operand could result in zero, null or an empty string and the like.

Example

class Foo
{
    public function bar($flag)
    {
        if ($foo = 'bar') { // possible typo
            // ...
        }
        if ($baz = 0) { // always false
            // ...
        }
    }
}

Source http://phpmd.org/rules/cleancode.html#ifstatementassignment

UnusedLocalVariable

Since: 0.2

Detects when a local variable is declared and/or assigned, but not used.

Example

class Foo {
    public function doSomething()
    {
        $i = 5; // Unused
    }
}

Source https://phpmd.org/rules/unusedcode.html#unusedlocalvariable

UnusedFormalParameter

Since: 0.2

Avoid passing parameters to methods or constructors and then not using those parameters.

Example

class Foo
{
    private function bar($howdy)
    {
        // $howdy is not used
    }
}

Source https://phpmd.org/rules/unusedcode.html#unusedformalparameter