Extra strict and opinionated rules for PHPStan

PHPStan focuses on finding bugs in your code. But in PHP there's a lot of leeway in how stuff can be written. This repository contains additional rules that revolve around strictly and strongly typed code with no loose casting for those who want additional safety in extremely defensive programming:

• Require booleans in if, elseif, ternary operator, after !, and on both sides of && and ||.
• Require numeric operands or arrays in + and numeric operands in -/*///**/%.
• Require numeric operand in $var++, $var--, ++$varand --$var.
• These functions contain a $strict parameter for better type safety, it must be set to true:
  • in_array (3rd parameter)
  • array_search (3rd parameter)
  • array_keys (3rd parameter; only if the 2nd parameter $search_value is provided)
  • base64_decode (2nd parameter)
• Variables assigned in while loop condition and for loop initial assignment cannot be used after the loop.
• Variables set in foreach that's always looped thanks to non-empty arrays cannot be used after the loop.
• Types in switch condition and case value must match. PHP compares them loosely by default and that can lead to unexpected results.
• Check that statically declared methods are called statically.
• Disallow empty() - it's a very loose comparison (see manual), it's recommended to use more strict one.
• Disallow short ternary operator (?:) - implies weak comparison, it's recommended to use null coalesce operator (??) or ternary operator with strict condition.
• Disallow variable variables ($$foo, $this->$method() etc.)
• Disallow overwriting variables with foreach key and value variables
• Always true instanceof, type-checking is_* functions and strict comparisons ===/!==. These checks can be turned off by setting checkAlwaysTrueInstanceof/checkAlwaysTrueCheckTypeFunctionCall/checkAlwaysTrueStrictComparison to false.
• Correct case for referenced and called function names.
• Correct case for inherited and implemented method names.
• Contravariance for parameter types and covariance for return types in inherited methods (also known as Liskov substitution principle - LSP)
• Check LSP even for static methods
• Require calling parent constructor
• Disallow usage of backtick operator ($ls = `ls -la`)
• Closure should use $this directly instead of using $this variable indirectly

Additional rules are coming in subsequent releases!

Installation

To use this extension, require it in Composer:

composer require --dev phpstan/phpstan-strict-rules

If you also install phpstan/extension-installer then you're all set!

Disabling rules

You can disable rules using configuration parameters:

parameters:
    strictRules:
        disallowedLooseComparison: false
        booleansInConditions: false
        uselessCast: false
        requireParentConstructorCall: false
        disallowedConstructs: false
        overwriteVariablesWithLoop: false
        closureUsesThis: false
        matchingInheritedMethodNames: false
        numericOperandsInArithmeticOperators: false
        strictCalls: false
        switchConditionsMatchingType: false
        noVariableVariables: false
        strictArrayFilter: false

Aside from introducing new custom rules, phpstan-strict-rules also change the default values of some configuration parameters that are present in PHPStan itself. These parameters are documented on phpstan.org.

Enabling rules one-by-one

If you don't want to start using all the available strict rules at once but only one or two, you can!

You can disable all rules from the included rules.neon with:

parameters:
    strictRules:
        allRules: false

Then you can re-enable individual rules with configuration parameters:

parameters:
    strictRules:
        allRules: false
        booleansInConditions: true

Even with strictRules.allRules set to false, part of this package is still in effect. That's because phpstan-strict-rules also change the default values of some configuration parameters that are present in PHPStan itself. These parameters are documented on phpstan.org.