如何在PHP中将函数转换为闭包？

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

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, ie 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

Answer 2

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 3

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);
};