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Extending the mysqli class

Hi everyone.

I am trying to create an extension of the mysqli class within PHP, and
I am finding it quite difficult. I am fairly new to PHP classes, and
decided to give them a go. Here's what I have to far:

class sql_db extends mysqli
var $connection = false;
function sql_db($usernam e, $password, $database="",
$server="localh ost")
$this->connection = new mysqli($server, $username,
$password, $database);
if (mysqli_connect _errno()) {
printf("Connect failed: %s\n",
mysqli_connect_ error());
return = $this->connection;

All I am trying to achieve for now is for a simple error to be printed
if the connection to the database fails. Rather than have error
checking for each within each PHP file, I would just like to have it
all done systematically. I would also like to add a few of my own
methods, such as having the object pass back a PHP array, rather than
a MySQL array. I know I can do this with a separate function, but
really I am doing this for the learning experience more than anything.

At the present time, this works:

$db =& new sql_db("myUsern ame", "myPass", "someDB");

But as soon as I try to query a table, like so:

$res = $db->query("SELEC T * FROM `some_table`;") ;

I get:

Warning: mysqli::query() : Couldn't fetch sql_db in - on line 21

Evidently I am doing something wrong, and I would really appreciate
any pointers. I suspect that I can't actually do what I want to do,
although I can't see why not. In any case, I am sure it's possible,
but I am going about it completely wrong.

Thanks in advance.


Feb 25 '07
21 7301
Daz wrote:
I am wondering why constructors are different in PHP5.
Under PHP 4:

class A
function A ()
print "Constructo r called\n";

class B extends A
// The constructor for this class is now a
// function called 'A'. If you were reading the
// code, this might be somewhat confusing, but
// you could logically infer that it's because
// it extends A.

class C extends B
// The constructor for this class is now a
// function called 'A'. There is no clue within
// this class definition as to why that is! If
// classes A and B were defined in a separate
// file, then there would be no clues in this
// file that the constructor function is called
// 'A'.

class D extends C
function D ()
print "This is D!\n";
parent::C(); // wrong!

PHP 5 allows all classes to have the same name for their constructor. So
when subclassing an existing class, you can reliably call the parent's
constructor function as "parent::__cont ruct()" without having to look into
the internals of the class that you're extending. (Which is how it should
be with OO programming: classes should be black boxes.)

Toby A Inkster BSc (Hons) ARCS
Contact Me ~ http://tobyinkster.co.uk/contact
Geek of ~ HTML/SQL/Perl/PHP/Python*/Apache/Linux

* = I'm getting there!
Feb 27 '07 #21
Michael Fesser wrote:
My scripts make use of many of the new OOP features in PHP 5, so they
won't run at all on PHP 4.

My current big pet project is http://demiblog.org/. This is PHP 5+ only
and supports MySQL 5+ and PostgreSQL 8+. Although I do realise that earlier
versions of these packages are still quite widely used out there, this
project probably won't hit the big 1.0 for another year or two, by which
time, the hosting world will have probably moved on a lot. Supporting
older versions of PHP and the database engines will cost development time
and push back the project release date even later, by which time PHP 4
support will be even less relevant.

So although PHP 4 may still be alive right now, it's counting down the
days to his retirement when it can hand over the family business to his
son PHP 5. He's heard the happy news that his dranddaughter PHP 6 is
planning on following in their footsteps too as soon as she graduates.
Because of PHP 4's impending retirements, he's not taking on any more big
projects at work, and is letting his son take on most of the new clients.

Analogy over, it would be unwise at this point to look at supporting PHP 4
for any medium-to-large projects that are starting now or in the future.
Existing PHP 4 projects should probably keep supporting PHP 4 for a while
yet, but should certainly make an effort to support PHP 5 as well, and
should be keeping a close eye on PHP 6 developments.

Toby A Inkster BSc (Hons) ARCS
Contact Me ~ http://tobyinkster.co.uk/contact
Geek of ~ HTML/SQL/Perl/PHP/Python*/Apache/Linux

* = I'm getting there!
Feb 27 '07 #22

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