PhpStorm 2017.3 Help

Extract Constant

Basics

The Extract Constant refactoring makes your source code easier to read and maintain. It also helps you avoid using hardcoded constants without any explanations about their values or purpose.

JavaScript example

BeforeAfter
Parenizor.method('toString', function () { return '(' + this.getValue() + ')'; } )
Parenizor.method('toString', function () { const string = '(' + this.getValue() + ')'; return string; } )

PHP examples

Extracting a class constant

When a constant is extracted within a class definition, the new constant is defined through the const keyword and referenced through the self keyword.

In PHP language version 7.1 and later, you can additionally mark the extracted constant as public, private, or protected.

BeforeAfter
class const_extraction { public static function find($params){ if (isset($params['param_query'])) { $result = MyDatabase::execute($params['param_query']); } } public static function findAll($params){ if (isset($params['param_query'])) { $result = MyDatabase::executeAll($params['param_query']); } } }
class const_extraction { const PARAM_QUERY = 'param_query'; public static function find($params){ if (isset($params[self::PARAM_QUERY])) { $result = MyDatabase::execute($params[self::PARAM_QUERY]); } } public static function findAll($params){ if(isset($params[self::PARAM_QUERY])){ $result = MyDatabase::executeAll($params[self::PARAM_QUERY]); } } }

Extracting a constant outside a class

When a constant is extracted outside a class definition, you can choose whether it will be defined through the const keyword or through the define() function.

BeforeAfter
<?php function find($params){ if (isset($params['param_query'])) { $result = MyDatabase::execute($params['param_query']); } } function findAll($params){ if (isset($params['param_query'])) { $result = MyDatabase::executeAll($params['param_query']); } }

const definition

<?php const PARAM_QUERY = 'param_query'; function find($params){ if (isset($params[PARAM_QUERY])) { $result = MyDatabase::execute($params[PARAM_QUERY]); } } function findAll($params){ if (isset($params[PARAM_QUERY])) { $result = MyDatabase::executeAll($params[PARAM_QUERY]); } }

Define() definition

<?php define('PARAM_QUERY', 'param_query'); function find($params){ if(isset($params[PARAM_QUERY])) { $result = MyDatabase::execute($params[PARAM_QUERY]); } } function findAll($params){ if(isset($params[PARAM_QUERY])) { $result = MyDatabase::executeAll($params[PARAM_QUERY]); } }

How to extract a constant

  1. In the editor, position the cursor inside the expression to be replaced with a constant.
  2. Choose Refactor | Extract Constant on the main menu or on the context menu of the selection. Alternatively pressCtrl+Alt+C.
  3. If a constant can be extracted from several expressions in the current context, PhpStorm shows all the relevant expressions in a pop-up list. Select the expression to apply the refactoring to.
  4. In the Extract Constant dialog box, type the name of the new constant in the Name text box.
  5. Specify the scope to apply refactoring in:
    • To have only the selected expression replaced, clear the Replace all occurrences checkbox.
    • To have PhpStorm replace the selected expression wherever it is used, select the Replace all occurrences checkbox.
  6. If the refactoring is invoked inside a class definition, choose the visibility scope (access level modifier) of the extracted constant. If you leave the default value selected, the constant will be implicitly defined as public without any modifier applied to it. Otherwise, you can choose the appropriate option to explicitly mark the constant as public, private, or protected.

    Setting visibility scope is only possible in PHP language version 7.1 and later. You can specify the PHP language level on the PHP page (File | Settings | Languages and Frameworks | PHP for Windows and Linux or PhpStorm | Preferences | Languages and Frameworks | PHP for macOS).

  7. If the refactoring is invoked outside a PHP class definition, choose the method to define the PHP constant in the Constant syntax area.
    • To have PhpStorm define the constant through the define() function, choose define.
    • To have PhpStorm define the constant through the const keyword outside a class definition, choose const.

      This method preserves the approach accepted in PHP version 5.3.0. Note that such constants are defined during compilation therefore they should be declared at the top-level scope but not inside functions, loops or if statements.

  8. Click OK to start the refactoring.
Last modified: 3 November 2017

See Also