PHP Closures/Lambdas for 5.2
A small experiment to providing closure-like capabilities in PHP 5.2. This is
a limited project and is only intended as a small polyfill-like solution for
those with PHP hosts that still do not provide 5.3+ and would like some of the
benefits of 5.3+'s closures (namely variable importing).
Note: this solution currently does not pass the imported variables by
reference.
Initialization
Either load the global lambda function from this project:
// Defines global function 'lambda'
// Usage: lambda($params);
include 'lambda-global.php';
Or load the local version into a variable:
// Defines local function $lambda
// Usage: $lambda($params);
$lambda = include 'lambda-local.php';
Syntax
$lambda(array(
'args' => array(/* */), // Arguments for the new function
'use' => array(/* */), // Variables to import into the scope of the function
'fn' => /* */, // Body of the function
));
Examples
Basic usage
// Define some variables
$x = 3;
$y = 4;
// Create a closure that uses $x and $y
$myClosure = $lambda(array(
'args' => array('$z'),
'use' => array('$x' => $x, '$y' => $y),
'fn' => 'return $z * $y * $z;'
));
$myClosure(5); // 60
External files
example.php
// Define some variables
$x = 3;
$y = 4;
// Create a closure that uses $x and $y
$myClosure = $lambda(array(
'args' => array('$z'),
'use' => array('$x' => $x, '$y' => $y),
'fn' => 'myclosure.php'
));
$myClosure(5); // 60
myclosure.php
<?php
// Having a separate file allows you to define the function without building
// your own unweildly string in the 'fn' argument
return $z * $y * $z;
Shorthands
// If $params[0] exists but not $params['fn'], $params['fn'] will take
// $params[0]'s value:
$callback = $lambda(array('use' => array('$stuff' => 3), '
var_dump($stuff);
'));
$callback(); // 3