Default "to" callback function

# UConverter::toUCallback

(PHP 5 >= 5.5.0, PHP 7, PHP 8, PECL >= 3.0.0a1)

UConverter::toUCallback — Default "to" callback function

### Description

public UConverter::toUCallback(
int `$reason`,
string `$source`,
string `$codeUnits`,
int `&$error`
): string|int|array|null

Warning

This function is currently not documented; only its argument list is available.

### Parameters

`reason`

`source`

`codeUnits`

`error`

### Return Values

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