passing multiple values to function

Anon

Hello there,

I'm trying to pass an array ($sessionsHeldArray)and a counter ($total) to a function.

my line of code is:
listSessions($sessionsHeldArray);

this will pass the array, but it's not possible to pass $total this way too is it??
listSessions($sessionsHeldArray, $total);

I didn't think that would be right...
See every time I go into the holdSession function I want another value to be inserted into the array, and for the counter to be added to.

Could I set up a class and keep track of the counter $total this way???

class counter{
var $total;

}

What would I call to add 1 to $total, and still access the $total count from both my functions?

Thanks so much!

maxholman

You can pass multiple variables to a function.

Your code...

listSessions($sessionsHeldArray, $total)

...would work perfectly with a function like...

function listSessions($array,$total) {
//some code
}

Anon

Thanks so much! Question for you if you don't mind.

I'm trying to pass all the values in the array back and forth between the 2 functions. That is what my $sessionsHeldArray was for.

so every time I go to my holdSession function I want to add another value to that array. Why isn't it passing the values in the array?

Thanks again!

Anon

Try doing this in the function definition:

function holdSession(&$array, $total){
//some code
}

The ampersand (&) in front of $array tells the function that the incoming variable $array is an array or an object. You will then be able to access the values in the array (or all properties and methods of an object, if you wanted to pass an object).

Also, if the function is to return the array, you will want to call the function like this:

$return_var = &holdSession($array, $total);
Hope this helps

Anon

thank you!!!!!!!!

mithril

John,

Umm... not to be technical or anything, but the ampersand doesn't indicate anything about the type of the variable that's being passed. The ampersand is the "pass by reference" operator in PHP (the equiv. of the asterisk in C), which is a pretty big difference. It is however most commonly used with array's and object's, so I can see why you might think that.

PHP by default copies and passes variables by value. In a nutshell, this means you get a fully independent copy of the original var, and the two vars are now separate entities each with their own memory space. When you pass by reference (ie. &$array), you telling the function to create a "link" to the original variable thus saving memory. However, passing by reference into a function is the same as declaring the variable global within that function.... just more elegant🙂. As such, an changed made to the $array variable within the holdSession() function will immediately appear in the original instance of $array. Therefore, you don't need to return it's value from that function.

Using this technique, you can make holdSession() increment and return your counter variable as well as modify the $array struct, and the rest of your script will have access to both modifications. However, global's and referenced variables can be a mixed blessing. Remember that any changes made reflect within the scope of the entire script, so make sure you are modifying and protecting for your data appropriately.

Hope this was a relatively clear explanation🙂 If not, drop me a line and I'll try to explain further. HTH.

geoff

mithril

Just to make a correction to an error I made in the previous point. Passing by reference (&) is not the equivalent of a C pointer (*). They both perform much the same functions and the difference is subtle, but I don't want to mislead anyone.

To quote from Ch. 14 of the PHP manual:

"References are a means in PHP to access the same variable content by different names. They are not like C pointers, they are symbol table aliases. Note that in
PHP, variable name and variable content are different, so the same content can have different names. The most close analogy is with Unix filenames and files -
variable names are directory entries, while variable contents is the file itself. References can be thought of as hardlinking in Unix filesystem."

C pointers reference directly to a specific memory location.

geoff

Anon

Yes, and I am aware of the distinction, since PHP is for the most part "typeless" (although not completely, as you can explicitely cast variables to specific types, and even explicitely check their types). I was hoping to make an association that was easy to understand - that referencing an array or object using & provides access to its own values, properties and methods. However, it was poorly worded, and I neglected to explain that without the & operator, a copy of the variable is created. I oversimplified. Sorry for the confusion.

Anon

hello there,

I'm trying to use the &$array thing to reference the array... I'm not sure if you remember replying to my problem last time but I still can't get it to work.

Do I need the array in a class?? Or do I need to make it global??

Right now I have:
function holdSessions(&$sessionsHeldArray, $total){
GLOBAL $dbName, $orgID, $sessionsHeldArray, $sessionID, $total;

$sessionsHeldArray[$total]="$sessionID";
$total++;
listSessions(&$sessionsHeldArray, $total);
}

Then in my listSessions function:

function listSessions(&$sessionsHeldArray, $total){
GLOBAL $dbName, $orgID, $sessionsHeldArray, $total;

print"<td valign=top><a href=\"sessions.php?section=holdSessions&total=$total&sessionsHeldArray=$sessionsHeldArray&sessionID=$sessionID&orgID=$orgID\">add to cart</a></td>

}

I want it so that when you click on the "add to cart link it takes the sessionID and puts it into the array.

If you could help it would be greatly appreciated!

mithril

Leena,

If you're passing the $sessionsHeldArray variable into the function by reference (which you are according to your code) you don't need to make it global or place it in a class. By passing it in by reference, you are in essence forcing it to be a global variable.

Since the passed array actually refers to the value of a copy of that array which exists outside the function, any changes made to the array inside the function will also be made to the array outside the function. This is, for the most part, what a global statement does.

In a class-based model, you would create the array in the constructor (or a Set() method) and then reference that value within the class's functions using the "$this->sessionsHeldArray" notation. The $this-> notation refers to the variable as global within the class's scope and serves much the same purpose as passing be reference or globalization does in a function based script. The main difference is you must have a class method which returns that array value in order to pass it to another class or a function outside the orignal class's scope.

Does this make sense? Clear as mud right?🙂 HTH, email me if you need further explanations or help on this topic.

geoff