Question

Recently i was studying the “Passing by Reference”, I come to know following ways

What is the main difference between the following methods.

1.

function foo(&$var)
{
    $var++;
}

$a=5;
foo($a);

2.

function foo($var)
{
    $var++;
}

$a=5;
foo(&$a);

3.

function foo(&$var)
{
    $var++;
}
function &bar()
{
    $a = 5;
    return $a;
}
foo(bar());

even though all of them produce same results, and which is the best way to work with.

Thanks.

Answer 1

function foo(&$var)
{
    $var++;
}

$a=5;
foo($a);

This accepts a parameter that is always passed by reference (the & is in foo(&$var)). When $a is passed, it’s always as a reference, so incrementing the variable inside the function will cause the parameter to be modified.

---

function foo($var)
{
    $var++;
}

$a=5;
foo(&$a);

Do not use this. This is call-time pass-by-reference (you’re passing &$a, a reference to $a, into the function), and is deprecated as of PHP 5.3.0. It’s bad practice because the function doesn’t expect a reference.

---

function foo(&$var)
{
    $var++;
}
function &bar()
{
    $a = 5;
    return $a;
}
foo(bar());

This returns a reference (the & is in &bar()) to a variable $a declared in the function bar(). It then takes a reference to the return value of bar() and increments it. I’m not sure at a glance why this would be useful, though, especially for primitive/scalar types.