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Extract parameter

Last modified: 27 December 2022

The Extract Parameter refactoring is used to add a new parameter to a function declaration and to update the function calls accordingly.

https://resources.jetbrains.com/help/img/idea/2022.3/ps_extract_parameter.png
Gif

Extract a PHP parameter in place

The in-place refactorings are enabled in PhpStorm by default. So, if you haven't changed this setting, the Extract Parameter refactorings for PHP are performed in-place, right in the editor:

  1. In the editor, position the caret within the expression to be replaced by the parameter.

  2. Do one of the following:

    • Press Ctrl+Alt+P.

    • Choose Refactor | Extract | Parameter from the main menu.

    • Choose Refactor | Extract | Parameter from the context menu.

  3. If more than one expression is detected for the current caret position, the Expressions list appears. If this is the case, click the expression to select it. Alternatively, press Up or Down to navigate to the expression of interest, and then press Enter to select it.

  4. Type the parameter name in the box with a red border.

  5. To complete the refactoring, press Tab or Enter.

    If you haven't completed the refactoring and want to cancel the changes you have made, press Escape.

    Note that sometimes you may need to press the corresponding key more than once.

Extract a parameter using the Extract Parameter dialog

To be able to use the Extract Parameter dialog (instead of performing the refactoring in-place), make sure that the Enable in place refactorings option is off in the editor settings.

Once this is the case, you perform the Extract Parameter refactoring as follows:

  1. In the editor, position the caret within the expression to be replaced by the parameter.

  2. Do one of the following:

    • Press Ctrl+Alt+P.

    • Choose Refactor | Extract | Parameter from the main menu.

    • Choose Refactor | Extract | Parameter from the context menu.

  3. If more than one expression is detected for the current caret position, the Expressions list appears. If this is the case, click the expression to select it. Alternatively, press Up or Down to navigate to the expression of interest, and then press Enter to select it.

  4. In the dialog that opens:

    1. Specify the parameter name in the Name field.

    2. If more than one occurrence of the expression is found within the function body, you can choose to replace only the selected occurrence or all the found occurrences with the references to the new parameter. Use the Replace all occurrences checkbox to specify your intention.

  5. Preview and apply changes.

PHP Example

In the example below, a new parameter $c is added to the Calculate() function to replace 10:

Before

After

class Class1 {
    public function Calculate($i){
        while ( $i < 10 ) {
            $i = $i + 1;
        };
        return $i;
    }

    public function DisplaySum(){
        $a = 1;
        $result = $this -> Calculate($a);
        echo "The final result is " . $result;
    }
}
class Class1 {
    public function Calculate($i,$c){
        while ( $i < $c ) {
            $i = $i + 1;
        };
        return $i;
    }

    public function DisplaySum(){
        $a = 1;
        $result = $this -> Calculate($a, 10);
        echo "The final result is " . $result;
    }
}

JavaScript Example

Before

After

A new parameter will be added to this function to replace the 1's: 

function calculate_sum(i) {
    alert('Adding ' + 1 + ' to ' + i);
    return (1 + i);
}

function show_sum() {
    alert('Result: ' + calculate_sum(5));
    }

The new parameter i2 has been added as an optional parameter: 

function calculate_sum(i, i2) {
    i2 = i2 || 1;
    alert('Adding ' + i2 + ' to ' + i);
    return (i2 + i);
}

function show_sum() {
// The function call has not changed:
    alert('Result: ' + calculate_sum(5));
}

A new parameter will be added to this function to replace the 1's. When adding a new parameter we'll specify that it should be a required one. 

function calculate_sum(i) {
    alert('Adding ' + 1 + ' to ' + i);
    return (1 + i);
}

function show_sum() {
    alert('Result: ' + calculate_sum(5));
}

The new parameter i2 has been added as a required parameter: 

function calculate_sum(i, i2) {
    alert('Adding ' + i2 + ' to ' + i);
    return (i2 + i);
}

function show_sum() {
    alert('Result: ' + calculate_sum(5, 1));
}

See Extract Parameter in JavaScript for details.

See also

Procedures