Page 198 - Beginning PHP 5.3

Part II: Learning the Language
Returning References from Your Own Functions

As well as passing variables by reference into functions, you can also get functions to return references,
rather than values. To do this, you place an ampersand before the function name in your function
definition. Then, when you return a variable with the return statement, you pass a reference to that
variable back to the calling code, rather than the variable ’ s value:

function & myFunc(){
// (do stuff)
return $var; // Returns a reference to $var

}
Here ’ s an example that shows return - by - reference in action:

$myNumber = 5;
function & getMyNumber() {
global $myNumber;
return $myNumber;
}

$numberRef = & getMyNumber();
$numberRef++;
echo “\$myNumber = $myNumber < br/ > ”; // Displays “6”
echo “\$numberRef = $numberRef < br/ > ”; // Displays “6”

Here ’ s how it works. First, a global variable, $myNumber , is created and given the value 5 . Next, a
function, getMyNumber() , is defined. This function simply uses the global keyword to access the
global variable $myNumber , then returns $myNumber . Because getMyNumber() has an ampersand before
its name, it returns a reference to $myNumber , rather than the value that $myNumber holds.

Next, the script calls getMyNumber() . The return value of getMyNumber() — that is, the reference to

$myNumber — is then assigned to a new variable, $numberRef . Notice the ampersand after the equals
sign; this ensures that $numberRef takes on the reference returned by getMyNumber() , rather than
taking on the value that the reference points to.
At this point, $numberRef and $myNumber both point to the same contents. To prove this, the code
increments $numberRef , then outputs the values of both $myNumber and $numberRef . Notice that they

both hold the same value — 6 — because they both point to the same piece of data.

Return - by - reference is used quite often in languages such as C++, because it ’ s the easiest way to return
complex data structures such as arrays and objects. However, because PHP lets you return pretty much
anything with its return statement, and automatically returns objects by reference anyway (as you see
in the next chapter), you probably won ’ t use return - by - reference that much in PHP.

Writing Recursive Functions

In Chapter 4 , you learned how to use loops to operate on large amounts of data at once. Looping is
often known as iteration .

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