Programming Tutorials

(追記) (追記ここまで)

use() in PHP

By: Anonymous in PHP Tutorials on 2011年10月29日 [フレーム]

use() parameters are early binding - they use the variable's value at the point where the lambda function is declared, rather than the point where the lambda function is called (late binding).

If you want late binding put & before the variable inside use()

<?php
$fn = function () use (&$var) { echo $var; };
?>

Examples:

<?php
// problem 1: this should echo "Canada", not a php notice
$fn = function () use ($country) { echo $country . "\n"; };
$country = 'Canada';
$fn();
// problem 2: this should echo "Canada", not "UnitedStates"
$country = 'UnitedStates';
$fn = function () use ($country) { echo $country . "\n"; };
$country = 'Canada';
$fn();
// problem 3: this should echo "Canada", not "UnitedStates"
$country = (object)array('name' => 'UnitedStates');
$fn = function () use ($country) { echo $country->name . "\n"; };
$country = (object)array('name' => 'Canada');
$fn();
// problem 4: this outputs "Canada". if this outputs "Canada",
// then so should problem 2 above. otherwise this should be
// just as broken as problem 2 and be outputting "UnitedStates"
$country = (object)array('name' => 'UnitedStates');
$fn = function () use ($country) { echo $country->name . "\n"; };
$country->name = 'Canada';
$fn();
?>



(追記) (追記ここまで)


Add Comment

JavaScript must be enabled for certain features to work
* Required information
1000

Comments

No comments yet. Be the first!

Most Viewed Articles (in PHP )

Latest Articles (in PHP)

(追記) (追記ここまで)
(追記) (追記ここまで)

AltStyle によって変換されたページ (->オリジナル) /