psalm/docs/running_psalm/issues/ParamNameMismatch.md

# ParamNameMismatch

Emitted when method overrides a parent method but renames a param.

```php
<?php

class A {
    public function foo(string $str, bool $b = false) : void {}
}

class AChild extends A {
    public function foo(string $string, bool $b = false) : void {}
}
```

## Why is this bad?

PHP 8 introduces [named parameters](https://wiki.php.net/rfc/named_params) which allow developers to call methods with explicitly-named parameters;

```php
<?php

function callFoo(A $a) {
    $a->foo(str: "hello");
}
```

In the first example passing `new AChild()` to `callFoo()` results in a fatal error, as AChild's definition of the method `foo()` doesn't have a parameter named `$str`.

## How to fix

You can change the child method param name to match:

```php
<?php

class A {
    public function foo(string $str, bool $b = false) : void {}
}

class AChild extends A {
    public function foo(string $str, bool $b = false) : void {}
}
```

## Workarounds

### @no-named-params

Alternatively you can ignore this issue by adding a `@no-named-params` annotation to the parent method:

```php
<?php

class A {
    /** @no-named-params */
    public function foo(string $str, bool $b = false) : void {}
}

class AChild extends A {
    public function foo(string $string, bool $b = false) : void {}
}
```

Any method with this annotation will be prevented (by Psalm) from being called with named parameters, so the original issue does not matter.

### Config allowInternalNamedParamCalls="false"

You can also set a config flag that tells Psalm to prohibit any named parameter calls on `@internal` classes or methods.

With that config value, this is now allowed:

```php
<?php

/**
 * @internal
 */
class A {
    public function foo(string $str, bool $b = false) : void {}
}

class AChild extends A {
    public function foo(string $string, bool $b = false) : void {}
}
```