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

TooManyFields

Since: 0.1

Classes that have too many fields could be redesigned to have fewer fields, possibly through some nested object grouping of some of the information. For example, a class with city/state/zip fields could instead have one Address field.

Example

class Person {
   protected $one;
   private $two;
   private $three;
   [... many more fields ...]
}

Source https://phpmd.org/rules/codesize.html#toomanyfields

ExcessivePublicCount

Since: 0.1

A large number of public methods and attributes declared in a class can indicate the class may need to be broken up as increased effort will be required to thoroughly test it.

Example

public class Foo {
    public $value;
    public $something;
    public $var;
    // [... more more public attributes ...]

    public function doWork() {}
    public function doMoreWork() {}
    public function doWorkAgain() {}
    // [... more more public methods ...]
}

Source https://phpmd.org/rules/codesize.html#excessivepubliccount

NPathComplexity

Since: 0.1

The NPath complexity of a method is the number of acyclic execution paths through that method. A threshold of 200 is generally considered the point where measures should be taken to reduce complexity.

Example

class Foo {
    function bar() {
        // lots of complicated code
    }
}

Source https://phpmd.org/rules/codesize.html#npathcomplexity

CyclomaticComplexity

Since: 0.1

Complexity is determined by the number of decision points in a method plus one for the method entry. The decision points are 'if', 'while', 'for', and 'case labels'. Generally, 1-4 is low complexity, 5-7 indicates moderate complexity, 8-10 is high complexity, and 11+ is very high complexity.

Example

// Cyclomatic Complexity = 11
class Foo {
1   public function example() {
2       if ($a == $b) {
3           if ($a1 == $b1) {
                fiddle();
4           } elseif ($a2 == $b2) {
                fiddle();
            } else {
                fiddle();
            }
5       } elseif ($c == $d) {
6           while ($c == $d) {
                fiddle();
            }
7        } elseif ($e == $f) {
8           for ($n = 0; $n < $h; $n++) {
                fiddle();
            }
        } else {
            switch ($z) {
9               case 1:
                    fiddle();
                    break;
10              case 2:
                    fiddle();
                    break;
11              case 3:
                    fiddle();
                    break;
                default:
                    fiddle();
                    break;
            }
        }
    }
}

Source https://phpmd.org/rules/codesize.html#cyclomaticcomplexity

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

LongVariable

Since: 0.2

Detects when a field, formal or local variable is declared with a long name.

Example

class Something {
    protected $reallyLongIntName = -3; // VIOLATION - Field
    public static function main( array $interestingArgumentsList[] ) { // VIOLATION - Formal
        $otherReallyLongName = -5; // VIOLATION - Local
        for ($interestingIntIndex = 0; // VIOLATION - For
             $interestingIntIndex < 10;
             $interestingIntIndex++ ) {
        }
    }
}

Source https://phpmd.org/rules/naming.html#longvariable

LongVariable

Since: 0.2

Detects when a field, formal or local variable is declared with a long name.

Example

class Something {
    protected $reallyLongIntName = -3; // VIOLATION - Field
    public static function main( array $interestingArgumentsList[] ) { // VIOLATION - Formal
        $otherReallyLongName = -5; // VIOLATION - Local
        for ($interestingIntIndex = 0; // VIOLATION - For
             $interestingIntIndex < 10;
             $interestingIntIndex++ ) {
        }
    }
}

Source https://phpmd.org/rules/naming.html#longvariable

LongVariable

Since: 0.2

Detects when a field, formal or local variable is declared with a long name.

Example

class Something {
    protected $reallyLongIntName = -3; // VIOLATION - Field
    public static function main( array $interestingArgumentsList[] ) { // VIOLATION - Formal
        $otherReallyLongName = -5; // VIOLATION - Local
        for ($interestingIntIndex = 0; // VIOLATION - For
             $interestingIntIndex < 10;
             $interestingIntIndex++ ) {
        }
    }
}

Source https://phpmd.org/rules/naming.html#longvariable

BooleanGetMethodName

Since: 0.2

Looks for methods named 'getX()' with 'boolean' as the return type. The convention is to name these methods 'isX()' or 'hasX()'.

Example

class Foo {
    /**
     * @return boolean
     */
    public function getFoo() {} // bad
    /**
     * @return bool
     */
    public function isFoo(); // ok
    /**
     * @return boolean
     */
    public function getFoo($bar); // ok, unless checkParameterizedMethods=true
}

Source https://phpmd.org/rules/naming.html#booleangetmethodname

BooleanGetMethodName

Since: 0.2

Looks for methods named 'getX()' with 'boolean' as the return type. The convention is to name these methods 'isX()' or 'hasX()'.

Example

class Foo {
    /**
     * @return boolean
     */
    public function getFoo() {} // bad
    /**
     * @return bool
     */
    public function isFoo(); // ok
    /**
     * @return boolean
     */
    public function getFoo($bar); // ok, unless checkParameterizedMethods=true
}

Source https://phpmd.org/rules/naming.html#booleangetmethodname