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

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

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

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

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

EmptyCatchBlock

Since: 2.7.0

Usually empty try-catch is a bad idea because you are silently swallowing an error condition and then continuing execution. Occasionally this may be the right thing to do, but often it's a sign that a developer saw an exception, didn't know what to do about it, and so used an empty catch to silence the problem.

Example

class Foo {

  public function bar()
  {
      try {
          // ...
      } catch (Exception $e) {} // empty catch block
  }
}

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

CamelCasePropertyName

Since: 0.2

It is considered best practice to use the camelCase notation to name attributes.

Example

class ClassName {
    protected $property_name;
}

Source

CamelCasePropertyName

Since: 0.2

It is considered best practice to use the camelCase notation to name attributes.

Example

class ClassName {
    protected $property_name;
}

Source

CamelCaseVariableName

Since: 0.2

It is considered best practice to use the camelCase notation to name variables.

Example

class ClassName {
    public function doSomething() {
        $data_module = new DataModule();
    }
}

Source

CamelCaseVariableName

Since: 0.2

It is considered best practice to use the camelCase notation to name variables.

Example

class ClassName {
    public function doSomething() {
        $data_module = new DataModule();
    }
}

Source

CamelCaseVariableName

Since: 0.2

It is considered best practice to use the camelCase notation to name variables.

Example

class ClassName {
    public function doSomething() {
        $data_module = new DataModule();
    }
}

Source

CamelCaseVariableName

Since: 0.2

It is considered best practice to use the camelCase notation to name variables.

Example

class ClassName {
    public function doSomething() {
        $data_module = new DataModule();
    }
}

Source

CamelCaseVariableName

Since: 0.2

It is considered best practice to use the camelCase notation to name variables.

Example

class ClassName {
    public function doSomething() {
        $data_module = new DataModule();
    }
}

Source

CamelCaseVariableName

Since: 0.2

It is considered best practice to use the camelCase notation to name variables.

Example

class ClassName {
    public function doSomething() {
        $data_module = new DataModule();
    }
}

Source

CamelCaseVariableName

Since: 0.2

It is considered best practice to use the camelCase notation to name variables.

Example

class ClassName {
    public function doSomething() {
        $data_module = new DataModule();
    }
}

Source