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Date: Fri, 4 Mar 2016 12:29:45 -0600
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Subject: Re: [PHP-DEV] Re: [RFC] Deprecations for PHP 7.1
From: me@stephencoakley.com (Stephen Coakley)

On 03/04/2016 07:53 AM, Johannes Schlüter wrote:
> On Thu, 2016-02-18 at 19:57 +0000, Andrea Faulds wrote:
>> I've actually used create_function on occasion for programmatically
>> generating functions (in particular to create a function for each PHP
>> operator), but it's trivially polyfillable, and it'd be better if
>> people
>> were implementing it themselves (and thus knowing it's based on
>> eval())
>> than using it directly without this knowledge.
>
> Just as a detail: You can't create a 100% compatible polyfill to
> create_function(). create_function() names functions starting with \0.
> Functions starting with \0 are hidden from get_defined_functions() and
> possibly other places.
>
> php > echo sizeof(get_defined_functions()['user']);
> 0
> php > create_function('', '');
> php > echo sizeof(get_defined_functions()['user']);
> 0
> php > eval('function foo() {}');
> php > echo sizeof(get_defined_functions()['user']);
> 1
>
> johannes
>

Good point. Another approach to a polyfill would be to use a closure then:

function create_function(string $args, string $code)
{
     return eval("return function($args) { $code };");
}

$newfunc = create_function('$a,$b', 'return "ln($a) + ln($b) = " . 
log($a * $b);');
echo $newfunc(2, M_E) . "\n";

Not a complete polyfill, since $newfunc is a closure and not a string, 
so you cannot print out the function name. I have no idea if any code 
relies on the lambda itself being a string though.

-- 
Stephen