How to Convert a Function into a Closure in PHP? - php

Question

I have function that uploads files to server:
function upload() {
$files = Input::file(self::$filename);
foreach ($files as $key => $file) {
// Validation
// Uploading
}
}
So, how to make this function as closure? That after loading it returns error or success information to output variable:
$results = function upload() {
}
In results should be result array of uploading files. It can be error or success state.

Answer 1

Since you're using self:: I assume you expect to run this function from inside a class. But you can't really do this - the function should be defined in the class to be able to use self::.
But really, you can just pass it as a parameter.
function upload($filename) {
$files = Input::file($filename); // note, self:: removed
foreach ($files as $key => $file) {
// Validation
// Uploading
}
return $result;
}
And when you need to use it inside your class, call it this way:
$result = upload(self::$filename);

Answer 2

For Converting a Function into a Closure in PHP, you can :
Since PHP 7 >= 7.1.0, you can use Closure::fromCallable()
$cl = Closure::fromCallable("upload");
$result = $cl();
Before (PHP >= 5.4.0), you can use ReflectionFunction::getClosure()
$reflexion = new ReflectionFunction('upload');
$cl = $reflexion->getClosure();
$result = $cl();
Another idea is to construct a new function that call your main function :
$cl = function (...$args) {
return upload(...$args);
};

Answer 3

Updated and Expanded
This answer addresses the OP's primary question of "How to Convert a Function into a Closure in PHP?" One way involves writing a nameless function and then assigning it to a variable. Since the OP's upload code is problematic, i.e. a method without a class, I therefore borrow the corrected code of #astax, modifying it for the purpose of illustrating the mechanics of how to create a closure in PHP, as follows:
<?php
$f = function( $filename ) {
$files = Input::file( $filename );
foreach ($files as $key => $file) {
// Validation
// Uploading
}
return $arrResults;
};
Note the trailing semicolon after the final brace. Also, the closure definition consists of an anonymous function. You may get the result as follows:
<?php
$arrResults = $f( $filename );
// or in a class:
$arrResults = $f( self::$filename );
Note: PHP does not have named closures, so the function needs to be anonymous. Usually it is assigned to a variable but PHP 7 provides more flexibility such that you may avoid setting a variable as the following two basic examples indicate:
<?php
echo (function() {
return 2 * 2;
})(),"\n",
(function(){
return function(){
return 3 * 3;
};
})()();
See live code.
This syntax is possible thanks to the support for function call chaining in PHP 7.
Note: if your code includes a return statement, when the closure executes, you may assign the return value to a variable.
Incidentally, two useful articles on PHP's closures: see this issue as well in this issue.
Lastly, note while other languages recognize a bound variable with a function as a closure and a nameless function as an anonymous function, in PHP support for each is done vis a vis the Closure class.
Caveat:
Care should be taken when creating a closure from the Closure object's fromCallable method since it evidently yields a more restricted closure as the following code demonstrates:
<?php
class A {
private $name;
public function __construct($name)
{
$this->name = $name;
}
}
$person = new A("Tim");
function test() {
return $this->name;
}
$f = function() {
return $this->name;
};
$cl = Closure::fromCallable( $f );
echo $cl->bindTo($person, 'A')();
echo "\n\nBut, Closure::fromCallable problematic:\n";
try {
$cl = Closure::fromCallable( "test" );
echo $cl->bindTo($person, 'A')();
} catch (Error $e) {
echo "Unable to bind closure from callable because: \n";
echo $e->getMessage();
}
see live code
The error message that results is as follows:
Warning: Cannot rebind scope of closure created by
ReflectionFunctionAbstract::getClosure() in /in/qso7b on line 26
Unable to bind closure from callable because: Function name must be a
string