[RESOLVED] OOP classes/functions help

MadMikeyB

I'm just trying to make a venture into OOP, the use of classes and functiones etc.

Here is my code so far, I don't know if database actions using classes/functions can be achieved better, I don't know if my functions work, the script simply whitepages on ?id=1 (which should say "mikey" in h1 tags.)

Like I say, I'm just starting to try to learn, so forgive me if I'm mixing procedural code in there with oop, and if there are better ways to achieve what I'm trying to do there (this is simply a test script so that I can learn)

Here is my current code:

<?php 

class dB 
{ 
    function connectDB($dbhost, $dbuser, $dbpass) 
    { 
        mysql_connect("$dbhost", "$dbuser", "$dbpass") or die(mysql_error()); 
    } 

function selectDB($dbname) 
{ 
    mysql_select_db("$dbname") or die(mysql_error()); 
} 

function fetchDB($sql) 
{ 
    if (!empty($sql)) { 
        $q = mysql_query($sql) or die(mysql_error()); 
        return mysql_fetch_assoc($q) or die(mysql_error()); 
    } else { 
        die("Error, empty query"); 
    } 
} 
} 

$dB = new dB(); 
$dB->connectDB("localhost", "db", "dbpass"); 
$dB->selectDB("db"); 


$id = (int)$_GET['id']; 
$user = $dB->fetchDB("SELECT * FROM `users` WHERE `userid` = '$id'"); 
// below does the same as above. below works. above does not.
    //$q = mysql_query("SELECT `username` AS 'name' FROM `users` WHERE `userid` = '$id';"); 
    //$user = mysql_fetch_assoc($q); 
    echo "<h1>{$user['username']}</h1>"; 

}

What's meant to happen is you visit script.php?id=1 and it will fetch id 1's username, and output it in H1 tags, It isnt doing this, and I think it is my fetchDB() function which is the cause of the problem.

Any help is appreciated 😃

bradgrafelman

The [man]mysql[/man] library is old and outdated, so newer projects shouldn't be using it. You might want to consider using [man]mysqli[/man] or [man]PDO[/man] instead.

As for your problem, you told us what it isn't doing yet you didn't tell us what it is doing. Do you have display_errors set to On and error_reporting set to E_ALL? If so, are you getting any PHP errors? Is the mysql_error() returning anything?

MadMikeyB

bradgrafelman;10971491 wrote:
The [man]mysql[/man] library is old and outdated, so newer projects shouldn't be using it. You might want to consider using [man]mysqli[/man] or [man]PDO[/man] instead.

Thanks, I'll look into using mysqli in future.

bradgrafelman;10971491 wrote:
As for your problem, you told us what it isn't doing yet you didn't tell us what it is doing.

It's simply white paging. No output is shown..

bradgrafelman;10971491 wrote:
Do you have display_errors set to On

Yes, it's set to on at the top of the script (I omitted it from this post as I considered it 'noise' not really needed to be included)

bradgrafelman;10971491 wrote:
and error_reporting set to E_ALL? If so, are you getting any PHP errors? Is the mysql_error() returning anything?

E_ALL and E_STRICT, no errors. mysql_error() isnt returning anything either.

When I var_dump($user) - I get boolean(true) (if I recall correctly)

bradgrafelman

MadMikeyB wrote:
It's simply white paging. No output is shown..

If you don't have any parse errors, then that's impossible - it should at least be outputting the static HTML from the echo statement. Perhaps you aren't viewing the source of the page if you're viewing it in a web browser?

MadMikeyB wrote:
Yes, it's set to on at the top of the script

Setting error reporting directives from within a script isn't recommended for development (or just about anything else, really), since a simple parse error will prevent those statements from ever executing (thus rendering them useless).

Have you verified (such as by doing a "lint check" - e.g. executing "php -l my_file.php" from the CLI) that your script has no parse errors?

MadMikeyB wrote:
When I var_dump($user) - I get boolean(true) (if I recall correctly)

Doubtful, since [man]mysql_fetch_assoc/man never returns boolean TRUE; might want to check again.

MadMikeyB

The script is located here; http://piefiles.com/test-oop.php?id=1

I've var_dump($user); again, and it's bool(true)

pie@aeon:~/public_html$ php -l test-oop.php
No syntax errors detected in test-oop.php

In the HTML it has the <h1> tags, just no record is being fetched from the db then..

jgetner

have you tried checking your database access information? or the tables names your are trying to retrieve from?

MadMikeyB

jgetner;10971513 wrote:
have you tried checking your database access information? or the tables names your are trying to retrieve from?

Yep, they're all correct, and when I run that query in PHPMyAdmin, It works (provided I substitute the id for a number, which the php script should be doing)

jgetner

then i would say it's not getting the correct input from the $_GET

MadMikeyB

jgetner;10971522 wrote:
then i would say it's not getting the correct input from the $_GET

I'm actually pretty sure it's the fetchDB(); function, as when I uncomment the commented out lines in the full script (at the top), and comment out the $dB->fetchDB(), it works as intended.

I'm not sure why anyway. I've been looking into the mysqli library and I see it already has classes to do what I'm trying to do here with MySQL.. (if I read correctly anyway)

Unplatoestrago

"return mysql_fetch_assoc($q) or die(mysql_error());"

The problem seems to be that you are trying to do a lot with the return. Try making that line into a variable like:

$result = mysql_fetch_assoc($q) or die(mysql_error());
return $result;

Then return the variable $result. As far as the error capturing you would be better suited using PHP's new exception handling or the like.

Unplatoestrago

You may also want to check out this individual post on checking for SQL errors

http://www.phpbuilder.com/board/showpost.php?p=10367121&postcount=15

laserlight

Unplatoestrago wrote:
"return mysql_fetch_assoc($q) or die(mysql_error());"

The problem seems to be that you are trying to do a lot with the return. Try making that line into a variable like:

$result = mysql_fetch_assoc($q) or die(mysql_error());
return $result;

Then return the variable $result.

That should not make a difference.

MadMikeyB

Unplatoestrago;10971555 wrote:
"return mysql_fetch_assoc($q) or die(mysql_error());"

The problem seems to be that you are trying to do a lot with the return. Try making that line into a variable like:

$result = mysql_fetch_assoc($q) or die(mysql_error());
return $result;

Then return the variable $result. As far as the error capturing you would be better suited using PHP's new exception handling or the like.

That fixed it..!

Strange how something so simple can put such a spanner in the works :/

Finished code is here; http://piefiles.com/test-oop.phps as you can see at http://piefiles.com/test-oop.php?id=1 - it worked fine.

Thanks everyone who helped me 🙂 And thanks for the recommendation of replacing my mysql usage with mysqli, I'm looking into that now.

bradgrafelman

laserlight;10971579 wrote:
That should not make a difference.

You wouldn't think so, at first glance, but my guess is that some grouping would have solved it, e.g.:

return (mysql_fetch_assoc($q) or die(mysql_error()));

EDIT: Then again, 'or die()' statements should never be in production-worthy code anyway, right? 😉

MadMikeyB

bradgrafelman;10971616 wrote:
EDIT: Then again, 'or die()' statements should never be in production-worthy code anyway, right? 😉

Yeah, of course, this script is just to test my understanding of OOP, I'm gonna buy this book which has been recommended on here too.

Unplatoestrago

I didn't think it mattered either but no matter where I tried it ( my localhost, an online code tester, and a production server), it didn't work for me. The code I supplied was the only way I could get it to work. Go figure.

laserlight

bradgrafelman wrote:
You wouldn't think so, at first glance, but my guess is that some grouping would have solved it, e.g.:

This can be tested:

<?php

function foo($x) {
    return ($x or die('error'));
}

if (foo(123) === 123) {
    echo 'pass';
} else {
    echo 'fail';
}

The result I get on PHP 5.3.2 is 'fail', indicating that grouping did not make a difference. In fact, I would expect this grouping to fail. The "correct" grouping of (return $x) or die('error') turns out to be a syntax error.

Unplatoestrago wrote:
I didn't think it mattered either but no matter where I tried it ( my localhost, an online code tester, and a production server), it didn't work for me. The code I supplied was the only way I could get it to work. Go figure.

The fact that bradgrafelman's grouping suggestion did not change anything implies that that is the grouping, i.e., ($x or die('error')) is evaluated as an expression (which in retrospect makes more sense than evaluating the return $x first). Since the result of an or expression is of boolean type, this explains MadMikeyB's problem: the array was always converted to boolean.