Problems with multidimensional arrays.

[OM2]

I have an array.

One of the items in the array is also an array.

 

I'm passing the array into a function.

The functions changes the contents of the array inside the array.

 

Problem: the changes only are visible inside the function.

Outside: there's no trace of the variables set inside the array's array.

 

I've tried adding the array's array into the function: but it doesn't like that!

 

My function decleration is something like this:

 

function myFunction($allVariables, $allVariables['subArray'])
{
//
}

 

What am I doing wrong...?

 

Thanks.

 

 

OM

[unkwntech]

It's the scope.  Variables inside the function are not accessible out side of it.

add this to the end of your function:

return $varName;

This will make it available outside the function

[Nhoj]

Any variables changed or declared inside a function stay inside the function. If you want to save the changes to $allVariales you would need to add:

 

return $allVariables;

 

at the end of the function before the last closing brace

[OM2]

guys: thanks for the lighting replies!

maybe i'm wrong, but i thought one of the advantages of using an array was that you could access items inside of them and change them?

 

previously, the same function used to only work with a single dimensional array.

this was accessed by calling global.

this worked fine.

but then i created an array and made it an array inside of a global array.

i then started passing in just the global array itself inside the function.

i was then referencing the array inside by myArray['var1']['subVar1'] etc.

 

i can pass a new variable back out - but i was sure that if u passed in a an array that u could manipulte its inside and that those changes were still valid outside?

 

let me know what u think.

 

thanks.

[Nhoj]

Unfortunately anything you pass into a function stay's in the function unless you return it at the end.

[OM2]

hmm... yes... i found that out by experimenting.

what threw me offline a little was when i used global: it works fine when i use this.

 

but, i'll do as u guys suggest and pass back a variable from the function.

actually... for that part... if i pass back an array, do all the values changed in the array stay?

what if my array was really huge?

does that mean a huge amount of data could potentially have to be passed through?

and therefore being inefficient - and therefore a good reason to use global?

 

let me know what you think.

thanks.

 

 

 

[Barand]

you can pass the array by reference instead of passing a copy of the aray

<?php
function double_it (&$array)                                     // function receives array by reference
{
    foreach ($array as $k=>$v) $array[$k] = $v * 2;
}

// call the function, passing the array

$ar = array (1,2,3);
double_it ($ar);

echo '<pre>', print_r($ar, true), '</pre>';
?>

gives -->

Array
(
    [0] => 2
    [1] => 4
    [2] => 6
)

[OM2]

hey thanks for that!

i was just about to give up and use global.

that works nicely.

[OM2]

actually... i just had a thought: is it a good idea to pass all gloabls varaibles by reference?

or is that just dangerous to do?

[Barand]

It's certainly a good idea to keep the use of globals to an absolute minimum, preferably zero. Better to pass them as args to functions. You only need to pass them by reference if you want to change their value in the function.

 

I also tend to pass arrays by ref, even when not updating their content, as it reduces memory usage. If you don't pass them by ref a copy is passed to the function, and with large arrays that's all extra memory and time.

[KevinM1]

Here's a quick question re: pass-by-reference...

 

In PHP 5, object assignment is automatically done by reference, correct?  So:

$obj1 = new Object();
$obj2 = $obj1;
$obj2->add(5);

//obj1 added 5 also, because they both reference the same object, right?

 

Does the same work for objects passed as arguments to another object's method?

//front controller code

$command = CommandResolver::getCommand($request); // <-- is $request a reference to the object, or a copy of it?

[Barand]

yes, passed by ref in v5. You have specifically to clone if you want a copy