PHP - Difference between 'use()' or 'global' to access a global variable in a closure?

问题

Is there any kind of performance or other difference between following two cases of accessing a global variable in a closure:

Case 1:

$closure = function() use ($global_variable) {
  // Use $global_variable to do something.
}

Case 2:

$closure = function() {
  global $global_variable; 
  // Use $global_variable to do something.
}

回答1:

There is an important difference between your two examples:

$global_variable = 1;

$closure = function() use ($global_variable) {
    return $global_variable; 
};

$closure2 = function() {
    global $global_variable;
    return $global_variable;
};

$global_variable = 99;

echo $closure();    // this will show 1
echo $closure2();   // this will show 99 

use takes the value of $global_variable during the definition of the closure while global takes the current value of $global_variable during execution.

global inherits variables from the global scope while use inherits them from the parent scope.

回答2:

Usekeyword are in parent scope, while global and $GLOBALS are from everywhere.

That's mean if you use global you may not know if the value have changed, from where by what and what is the kind of the change.

You have more control by using use. So it depends on your needs.

来源：https://stackoverflow.com/questions/39741443/php-difference-between-use-or-global-to-access-a-global-variable-in-a-cl