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

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

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

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

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

ExitExpression

Since: 0.2

An exit-expression within regular code is untestable and therefore it should be avoided. Consider to move the exit-expression into some kind of startup script where an error/exception code is returned to the calling environment.

Example

class Foo {
    public function bar($param)  {
        if ($param === 42) {
            exit(23);
        }
    }
}

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

ShortVariable

Since: 0.2

Detects when a field, local, or parameter has a very short name.

Example

class Something {
    private $q = 15; // VIOLATION - Field
    public static function main( array $as ) { // VIOLATION - Formal
        $r = 20 + $this->q; // VIOLATION - Local
        for (int $i = 0; $i < 10; $i++) { // Not a Violation (inside FOR)
            $r += $this->q;
        }
    }
}

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