I know you can do: $hash('foo')
and $$foo
and also $bar[$foo]
, what are each of these things called?
views:
108answers:
1
+17
A:
$hash('foo')
is a variable function.
$hash
may contain a string with the function name, or an anonymous function.$hash = 'md5'; // This means echo md5('foo'); // Output: acbd18db4cc2f85cedef654fccc4a4d8 echo $hash('foo');
$$foo
is a variable variable.
$foo
may contain a string with the variable name.$foo = 'bar'; $bar = 'baz'; // This means echo $bar; // Output: baz echo $$foo;
$bar[$foo]
is a variable array key.
$foo
may contain anything that can be used as an array key, like a numeric index or an associative name.$bar = array('first' => 'A', 'second' => 'B', 'third' => 'C'); $foo = 'first'; // This tells PHP to look for the value of key 'first' // Output: A echo $bar[$foo];
The PHP manual has an article on variable variables, and an article on anonymous functions (but I didn't show an example above for the latter).
BoltClock
2010-09-05 07:48:02
wow, I got it correct by guessing. Can you cite this though?
Johnny
2010-09-05 07:49:01
Variable array keys are pretty staple. I've included the PHP manual links for variable variables and variable functions.
BoltClock
2010-09-05 07:57:13
Things get really funny if you use the extended variable syntax. This allows stuff like `${'prefix_' . $name}` or even funnier things like `${$var = 'var'}` (this is `'var'`).
nikic
2010-09-05 08:17:28
+1: "Variable function" calls can also be used on objects that declare an `__invoke` magic method (Since PHP 5.3). So it can handle string function names, the return from `create_function()`, a `Closure` object (which is created when you use anonymous functions since 5.3) or a generic object which declares a `__invoke` method. It's too bad you can't use it on other callback types (`array('classname', 'methodname')`)...
ircmaxell
2010-09-05 08:37:36
Is someone jealous? :)
BoltClock
2010-10-23 07:32:13