PHP variables in anonymous functions

Question

I was playing around with anonymous functions in PHP and realized that they don't seem to reach variables outside of them. Is there any way to get around this problem?

Example:

$variable = "nothing";

functionName($someArgument, function() {
  $variable = "something";
});

echo $variable;  //output: "nothing"

This will output "nothing". Is there any way that the anonymous function can access the $variable?

Solution 1

Yes, use a closure:

functionName($someArgument, function() use(&$variable) {
  $variable = "something";
});

Note that in order for you to be able to modify $variable and retrieve the modified value outside of the scope of the anonymous function, it must be referenced in the closure using &.

Solution 2

If your function is short and one-linear, you can use arrow functions, as of PHP 7.4:

$variable = "nothing";
functionName($someArgument, fn() => $variable = "something");

Comments

[gen_Eric]

It's new! It's syntax that's new in PHP 5.3.

[DaveRandom]

@Rocket So, to be fair, is the true anonymous function syntax (as opposed to create_function()) and the use keyword is documented (badly) on the same doc page that describes them.

[keyboardSmasher]

Quick note for those who may not know: You can drop the & when passing an object, since they are always passed by reference...and don't forget your type-hint :) E.g.: function() use (PDO $pdo) {

[nickb]

@Alliswell No, it's only for objects, otherwise you need to pass by reference to modify the variable. See this example.