In PHP, what is a closure and why does it use the “use” identifier?

Question

I\'m checking out some PHP 5.3.0 features and ran across some code on the site that looks quite funny:

public function getTotal($tax)
{
    $tot         


        

Answer 1

Zupa did a great job explaining closures with 'use' and the difference between EarlyBinding and Referencing the variables that are 'used'.

So I made a code example with early binding of a variable (= copying):

";
    echo "Inside \$closureExampleEarlyBinding() \$b = ".$b."
";    
};

echo "Before executing \$closureExampleEarlyBinding() \$a = ".$a."
";
echo "Before executing \$closureExampleEarlyBinding() \$b = ".$b."
";  

$closureExampleEarlyBinding();

echo "After executing \$closureExampleEarlyBinding() \$a = ".$a."
";
echo "After executing \$closureExampleEarlyBinding() \$b = ".$b."
";

/* this will output:
Before executing $closureExampleEarlyBinding() $a = 1
Before executing $closureExampleEarlyBinding() $b = 2
Inside $closureExampleEarlyBinding() $a = 2
Inside $closureExampleEarlyBinding() $b = 3
After executing $closureExampleEarlyBinding() $a = 1
After executing $closureExampleEarlyBinding() $b = 2
*/

?>

Example with referencing a variable (notice the '&' character before variable);

";
    echo "Inside \$closureExampleReferencing() \$b = ".$b."
"; 
};

echo "Before executing \$closureExampleReferencing() \$a = ".$a."
";
echo "Before executing \$closureExampleReferencing() \$b = ".$b."
";   

$closureExampleReferencing();

echo "After executing \$closureExampleReferencing() \$a = ".$a."
";
echo "After executing \$closureExampleReferencing() \$b = ".$b."
";    

/* this will output:
Before executing $closureExampleReferencing() $a = 1
Before executing $closureExampleReferencing() $b = 2
Inside $closureExampleReferencing() $a = 2
Inside $closureExampleReferencing() $b = 3
After executing $closureExampleReferencing() $a = 2
After executing $closureExampleReferencing() $b = 3
*/

?>