Question

In PHP you have the create_function() function which creates a unique named lambda function like this:

$myFunction = create_function('$foo', 'return $foo;'); $myFunction('bar'); //Returns bar 

Is this actually any better (apart from being more easy) then just doing:

do{  $myFunction = 'createdFunction_'.rand(); } while(function_exists($myFunction)); eval('function $myFunction(\$foo) { return \$foo; }'); $myFunction('bar'); //Returns bar 

Is create_function really better? (apart from the fact that it is more easy)

Answer 1

On my understanding of the relevant docs,[1] they both do the same thing, create_function() just comes up with a unique function name for you.

To address some other comments on this question:

create_function can be assigned to a variable making the function accessible to other parts of your code, whereas eval is only useful for the given scope.

It may well be that eval() runs in the current scope, but function definitions get dumped into the global namespace anyway.[2] So whenever you define a function, it will be accessible everywhere else in your program.

Using eval() will clutter the global function list, create_function() will not

create_function() only returns a string with the name of the new function,[3] not some special callback type. So, both techniques will pollute your global namespace.

So no, apart from create_function() being easier, it does not appear to be any better than eval().

Footnotes:

[1] https://www.php.net/manual/en/functions.user-defined.php ; http://au.php.net/create_function ; http://au.php.net/eval

[2] https://www.php.net/manual/en/functions.user-defined.php

[3] http://au.php.net/create_function