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

UndefinedVariable

Since: 2.8.0

Detects when a variable is used that has not been defined before.

Example

class Foo
{
    private function bar()
    {
        // $message is undefined
        echo $message;
    }
}

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

BooleanArgumentFlag

Since: 1.4.0

A boolean flag argument is a reliable indicator for a violation of the Single Responsibility Principle (SRP). You can fix this problem by extracting the logic in the boolean flag into its own class or method.

Example

class Foo {
    public function bar($flag = true) {
    }
}

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

BooleanArgumentFlag

Since: 1.4.0

A boolean flag argument is a reliable indicator for a violation of the Single Responsibility Principle (SRP). You can fix this problem by extracting the logic in the boolean flag into its own class or method.

Example

class Foo {
    public function bar($flag = true) {
    }
}

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

BooleanArgumentFlag

Since: 1.4.0

A boolean flag argument is a reliable indicator for a violation of the Single Responsibility Principle (SRP). You can fix this problem by extracting the logic in the boolean flag into its own class or method.

Example

class Foo {
    public function bar($flag = true) {
    }
}

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

BooleanArgumentFlag

Since: 1.4.0

A boolean flag argument is a reliable indicator for a violation of the Single Responsibility Principle (SRP). You can fix this problem by extracting the logic in the boolean flag into its own class or method.

Example

class Foo {
    public function bar($flag = true) {
    }
}

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

ErrorControlOperator

Error suppression should be avoided if possible as it doesn't just suppress the error, that you are trying to stop, but will also suppress errors that you didn't predict would ever occur. Consider changing error_reporting() level and/or setting up your own error handler.

Example

function foo($filePath) {
    $file = @fopen($filPath); // hides exceptions
    $key = @$array[$notExistingKey]; // assigns null to $key
}

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

BooleanArgumentFlag

Since: 1.4.0

A boolean flag argument is a reliable indicator for a violation of the Single Responsibility Principle (SRP). You can fix this problem by extracting the logic in the boolean flag into its own class or method.

Example

class Foo {
    public function bar($flag = true) {
    }
}

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

ElseExpression

Since: 1.4.0

An if expression with an else branch is basically not necessary. You can rewrite the conditions in a way that the else clause is not necessary and the code becomes simpler to read. To achieve this, use early return statements, though you may need to split the code it several smaller methods. For very simple assignments you could also use the ternary operations.

Example

class Foo
{
    public function bar($flag)
    {
        if ($flag) {
            // one branch
        } else {
            // another branch
        }
    }
}

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

ElseExpression

Since: 1.4.0

An if expression with an else branch is basically not necessary. You can rewrite the conditions in a way that the else clause is not necessary and the code becomes simpler to read. To achieve this, use early return statements, though you may need to split the code it several smaller methods. For very simple assignments you could also use the ternary operations.

Example

class Foo
{
    public function bar($flag)
    {
        if ($flag) {
            // one branch
        } else {
            // another branch
        }
    }
}

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

ElseExpression

Since: 1.4.0

An if expression with an else branch is basically not necessary. You can rewrite the conditions in a way that the else clause is not necessary and the code becomes simpler to read. To achieve this, use early return statements, though you may need to split the code it several smaller methods. For very simple assignments you could also use the ternary operations.

Example

class Foo
{
    public function bar($flag)
    {
        if ($flag) {
            // one branch
        } else {
            // another branch
        }
    }
}

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

ElseExpression

Since: 1.4.0

An if expression with an else branch is basically not necessary. You can rewrite the conditions in a way that the else clause is not necessary and the code becomes simpler to read. To achieve this, use early return statements, though you may need to split the code it several smaller methods. For very simple assignments you could also use the ternary operations.

Example

class Foo
{
    public function bar($flag)
    {
        if ($flag) {
            // one branch
        } else {
            // another branch
        }
    }
}

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

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