[RESOLVED] Why the result of my code is not as I expect

adcoder

Hello everyone.
This is adcoder, a brand new member of the world of phpbuilder. Hoooo. How excited I was when i was surfing this site when i was thinking to jump into the world of web development. And today I am here.

I have no solid background of web development and php and other web development languages.

While in the meanwhile i found a book which is very brief but many things are discussed in it. Here i am here with a code where function is using with local and global variables; that how to use a global variable inside a local function by using global keyword.

Here is the code:

$number = 50;
function tenTimes() {

global $number;
$number = $number * 10;
}

tenTimes();
echo $number;

I was expecting that this code result will be 50 because i thought that

$number = 50;

is globally declared and it is also used inside the function but in the function there is no echo or print statement and the only echo statement outside the body of the function will just output the 50 but the result is 500.

Why the result is 500 instead of 50? Even there is no echo statement inside the function body?

Thanks

dalecosp

Textbook stuff here.

PHP Manual wrote:
By declaring $a and $b global within the function, all references to either variable will refer to the global version.

Variable Scope --- see the 3rd code block/example.

adcoder

Thank you dalecosp:

Please make me correct if I am wrong with my clarification:
From the definition of the 3rd code block example what i inferred is:

That I declare a variable (as in post # 1 $number) globally and then I use it inside the function (tenTimes()) by using the global keyword, from now on all the changes I will make to that particular variable will actually be reflected on the original global variable (which is defined globally/ outside of function i.e. [noparse]$number = 50;[/noparse]), even it has a specific value just like it has in my example.

Am I right with this understanding?

Thanks.

adcoder

Oohh. I put the semi colon (php statement termination symbol) and closed the parenthesis and it turned into smiley, Sorry. Can't I edit my post. It may change the meaning of my reply.

Moderator please guide me here. It's just my 2nd time to log in to this site I don't know that there is edit option. Can you correct it please?

NogDog

When posting code, just stick it inside of [noparse][/code]...[/code][/noparse] tags, like this:

<?php
echo "Hello, World!";

See http://board.phpbuilder.com/misc.php?do=bbcode for other fun BBCode tag options.

PS: I added some "noparse" tags so that you no longer get that annoying smiley.

NogDog

And your understanding is now correct about global. That being said, using global within a function is highly frowned upon, because it tightly couples the function to the code it works with, and it can lead to difficult to find bugs. So, it's good to understand it for when you run into it being used somewhere (in code you didn't write!), but you should avoid using it. Instead, pass variables into the function as parameters, and return whatever value you need, and when that's not sufficient, you can pass variables by reference into a function (I'll let you google that), which is sort of like making the passed variable global within the function, with the difference that it's more readily apparent to the code calling the function that this is happening.

dalecosp

adcoder;11052655 wrote:
Oohh. I put the semi colon (php statement termination symbol) and closed the parenthesis and it turned into smiley, Sorry. Can't I edit my post. It may change the meaning of my reply.

Moderator please guide me here. It's just my 2nd time to log in to this site I don't know that there is edit option. Can you correct it please?

If you keep coming here and posting, sooner or later you will have an edit option (you have to have a minimum post count of $n, which is a fairly low integer, I think), but even for us with hundreds/thousands of posts the edit link is only available for a limited time after the post has been made.

Oh, and welcome to PHPBuilder!!! 🙂

adcoder

NogDog;11052661 wrote:
And your understanding is now correct about global. That being said, using global within a function is highly frowned upon, because it tightly couples the function to the code it works with, and it can lead to difficult to find bugs. So, it's good to understand it for when you run into it being used somewhere (in code you didn't write!), but you should avoid using it. Instead, pass variables into the function as parameters, and return whatever value you need, and when that's not sufficient, you can pass variables by reference into a function (I'll let you google that), which is sort of like making the passed variable global within the function, with the difference that it's more readily apparent to the code calling the function that this is happening.

Thank you NogDog, for guiding me. As I am brand new to php world so i found some book where it is given an example for understanding by the user but he has not given any explanation, which caused to me ask here. But as you said that using this method is not a good skill, so I will surely not use it.

I am learning function parameter passing and returning values.

and Thanks for jumping into my thread regarding my problem.

adcoder

thanks for guiding me with my queries.