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Doc Bug #80032 Can't use valid callback as default value for callable parameters
Submitted: 2020-08-28 19:16 UTC Modified: 2020-10-11 04:22 UTC
From: antonfedonyuk at gmail dot com Assigned: cmb (profile)
Status: No Feedback Package: *General Issues
PHP Version: 7.4.9 OS: Any
Private report: No CVE-ID: None
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 [2020-08-28 19:16 UTC] antonfedonyuk at gmail dot com
Can't use valid callback(string or array) as default value of callable parameters. It's generate fatal error: Default value for parameters with callable type can only be NULL. The guide doesn't contain any notes on this issue.

Test script:
function test(callable $callback = 'strtoupper')
   return $callback();


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 [2020-08-28 21:01 UTC]
-Status: Open +Status: Verified -Type: Bug +Type: Documentation Problem -Package: Compile Failure +Package: *General Issues
 [2020-09-30 12:19 UTC]
-Status: Verified +Status: Feedback -Assigned To: +Assigned To: cmb
 [2020-09-30 12:19 UTC]
The manual states[1]:

| A function may define C++-style default values for scalar
| arguments as follows:

Since callables are not scalar, is there anything to add?

[1] <>
 [2020-09-30 15:37 UTC] antonfedonyuk at gmail dot com
-Status: Feedback +Status: Assigned
 [2020-09-30 15:37 UTC] antonfedonyuk at gmail dot com iterable not scalar too
 [2020-09-30 15:47 UTC]
-Status: Assigned +Status: Feedback
 [2020-09-30 15:47 UTC]
> iterable not scalar too

Well, the documentation mentions after the scalar examples:

| PHP also allows the use of arrays and the special type NULL as
| default values, […]
 [2020-10-11 04:22 UTC] php-bugs at lists dot php dot net
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