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IX. Funkce pro pr�ci s t��dami/objekty
Tyto funkce v�m umo��uj� z�sk�vat informace o t��d�ch a instanc�ch. M��ete
zjistit n�zev t��dy do kter� objekt pat�� nebo jeho prom�nn� a metody.
Pomoc� t�chto funkc� m��ete zjistit nejen p��slu�nost objektu k t��d�,
ale i jeho p�edka (tj. kterou t��du t��da tohoto objektu roz�i�uje).
Tyto funkce jsou k dispozici jako sou��st
standardn�ho modulu, kter� je v�dy dostupn�. K pou��v�n� t�chto funkc� nen� t�eba ��dn�
instalace, jsou sou��st� j�dra PHP. Toto roz���en� nem� definov�no ��dn� konfigura�n�
direktivy. Toto roz���en� nem� definov�n ��dn� typ prost�edku
(resource). Toto roz���en� nem� definov�ny ��dn�
konstanty.
V t�to uk�zce nejd��ve definujeme z�kladn� t��du a roz���en� t�to t��dy.
Z�kladn� t��da popisuje obecnou zeleninu, a� u� je jedl� nebo ne a bez
ohledu na jej� barvu. Podt��da Spenat p�id�v� metodu
na uva�en� t�to zeleniny a dal��, kter� zjist�, jestli je va�en�.
P��klad 1. classes.inc |
<?php
class Zelenina {
var $jedla;
var $barva;
function Zelenina( $jedla, $barva="green" ) {
$this->jedla = $jedla;
$this->barva = $barva;
}
function je_jedla() {
return $this->jedla;
}
function jaka_barva() {
return $this->barva;
}
} class Spenat extends Zelenina {
var $varena = false;
function Spenat() {
$this->Zelenina( true, "zelena" );
}
function cook_it() {
$this->varena = true;
}
function je_varena() {
return $this->varena;
}
} ?>
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Potom z t�chto t��d vytvo��me 2 objekty a vytiskneme informace o nich, v�.
rodi�ovsk�ch t��d. Tak� definujeme n�kter� pomocn� funkce, p�edev��m kv�li
pohodln�mu tisku informac�.
P��klad 2. test_script.php |
<pre>
<?php
include "classes.inc";
function vytiskni_promenne($obj) {
$pole = get_object_vars($obj);
while (list($vlastnost, $hodnota) = each($pole))
echo "\t$vlastnost = $hodnota\n";
}
function vytiskni_metody($obj) {
$pole = get_class_methods(get_class($obj));
foreach ($pole as $metoda)
echo "\tfunction $metoda()\n";
}
function class_parentage($obj, $class) {
if (is_subclass_of($GLOBALS[$obj], $class)) {
echo "Objekt $obj pat�� do t��dy ".get_class($$obj);
echo ", kter� je podt��dou $class\n";
} else {
echo "Objekt $obj nepat�� do podt��dy t��dy $class\n";
}
}
$zeleninka = new Zelenina(true,"modr�");
$listnaty = new Spenat();
echo "zeleninka: CLASS ".get_class($zeleninka)."\n";
echo "listnat�: CLASS ".get_class($listnaty);
echo ", PARENT ".get_parent_class($listnaty)."\n";
echo "\nzeleninka: Vlastnosti\n";
vytiskni_promenne($zeleninka);
echo "\nlistnat�: Metody\n";
vytiskni_metody($listnaty);
echo "\nRodi�:\n";
class_parentage("listnaty", "Spenat");
class_parentage("listnaty", "Zelenina");
?>
</pre>
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Je t�eba poznamenat, �e ve v��e uveden� uk�zce je objekt
$listnaty instanc� t��dy Spenat,
kter� je podt��dou t��dy Zelenina, a posledn� ��st
v��e uveden�ho skriptu tud� vytiskne:
[...]
Rodi�:
Objekt listnaty nepat�� do podt��dy t��dy Spenat
Object listnaty pat�� do t��dy Spenat, kter� je podt��dou Zelenina |
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 add a note
User Contributed Notes
Funkce pro pr�ci s t��dami/objekty
iparanoid at gmx dot de
04-Aug-2004 06:17
To pillepop2003 at yahoo dot de:
It seems to me if there really is no nice way to get the class name in an un-instanciated class, there is a workaround in PHP5 though using static/class variables.
Example:
<?php
class myFoo
{
static $__ClassName = __CLASS__;
static function getClassName()
{
return myFoo::$__ClassName;
}
};
class myFooExtended extends myFoo
{
function __construct()
{
myFooExtended::$__ClassName = __CLASS__;
};
};
?>
However, you'll need to have at least instanciated an object of the class myFooExtended before calling getClassName or introduce some other initialization (the class variable will need to be set at some point to __CLASS__ in the sub-class).
greg at doutromundo dot com
06-Jul-2004 02:58
As programmers, you're probably more organized than me, but, I do try and maintain some order in my classes and codes and separate them in "packages" as in java.
This helped me keep them organized but caused havok when trying to use them, so what I did was to create a class that handles the loading of classes (which I instanciate in all pages) along with my error handling class all bundled up. This way, I can load my classes with a command similar to
$baseClass->loadClass("package","className"[,"constructor"]);
the function responsible for this has some checking to see if they are loaded and stuff like that...
function loadClass($packageName,$className,$constructor=""){
// if you dont have a constructor declare any function inside
// the class
if ($constructor==""){
$constructor=$className;
}
if(!is_callable(array($className,$constructor))){
if (defined("CLASS_DIR")){
$pkg = CLASS_DIR.$packageName."/";
if (is_dir($pkg)){
// we have a directory with the package name
$cls = $pkg.$className.".class.php";
if(is_file($cls)){
// we have a file
include_once($cls);
}else{
die("Class <b>$className</b> could not be found in package <b>$packageName</b> , please check your instalation");
}
}else{
die("Package <b>$packageName</b> could not be found, please check your instalation");
}
}
}
}
Just remember to define CLASS_DIR as the physical path for the directories where you packages are...
Hope this comes in handy...
Here's an example of a diretory strucutre...
/var/www/classes/ <- this would be CLASS_DIR
in there I have:
package1/
name.class.php
name2.class.php
....
The loadClass would look like: loadClass("package1","name");
Cute and easy
ettinger at consultant dot com
18-Jun-2004 11:59
Re: Looking for an uninstantiated class
# Loads data from a table into a class object
class LFPDataFactory extends LFPObject {
var $object;
var $class;
var $table;
function LFPDataFactory($args) {
$this->unpackArgs($args); // assigns locals from $args
if (in_array(strtolower($this->class), get_declared_classes())) {
$this->object = new $this->class;
// assemble the columns in the table...
// select their values and put them in our new object...
} else { trigger_error("Class ".$this->class." not found", E_USER_ERROR); }
}
}
$r = new LFPDataFactory("class=LFPLayout,table=layout");
$new_obj = $r->object; // this is a LFPLayout object.
print_r($new_obj);
This class looks to see if the class exists, then instantiates it -- a declared class is not the same as an instantiated class. As long as LFPLayout exists somewhere in the scripts, get_declared_classes() will find it. Remember strtolower on compare, however.
Why would I do this? Because I have my class layouts the same as their respective tables; the factory then selects the data (making sure that the variables match) and plugs in the data. (I've left out the actual code to do the selection/insertion).
brett_hegr xATx yahoo xDOTx com
10-Jun-2004 12:46
// Useful function for determining if an object is either an
// instance or a subclass of a particular class.
function is_class($object,$class_name)
{
$parent = is_a($object, $class_name);
$child = is_subclass_of($object, $class_name);
return $parent xor $child;
}
HOC
28-May-2004 04:40
to pillepop2003
Why do u want to know the classname of an non-existant object?
The only possible explanation for this question seems to me u want to know the class before u instantiate the object. Well, this is of no use since u always instantiate a class of ur choice.
When the class is instantiated into an object u can find the class of the object by means of get_class(). This is all u need. In case of inheritance u can use get_class($this) to get the class of the instantiated object. Now u can differentiate according to which class the object belongs to.
e.g.:
<?php
class A{
function A(){
$class_of_this = get_class($this);
echo 'Object is an instance of class '.$class_of_this.' which is the ';
if(strcmp($class_of_this,'A')==0)
echo 'parent-class';
else if(strcmp($class_of_this,'B')==0)
echo 'child-class';
echo ".\n";
}
}
class B extends A{
function B(){
$this->A();
}
}
$object1 = new A();
$object2 = new B();
?>
When u run this code-snippet the output will be:
Object is an instance of class A which is the parent-class.
Object is an instance of class B which is the child-class.
pillepop2003 at yahoo dot de
26-May-2004 05:05
I spent several hours finding out, that there seems to be no way to determine the name of an uninstantiated class.
e.g. you can't do anything like
class_b::give_me_ur_name();
where give_me_ur_name() should return "class_b".
(This is a lack, cos' it can be important to determine the classes' name when u use inherited objects...)
mfirat at fibronline dot com
02-Apr-2004 01:18
<?php
class calculator {
var $c;
function addition($a, $b) {
$this->c = $a + $b;
return $this->c;
}
function subtraction($a, $b) {
$this->c = $a - $b;
return $this->c;
}
function multiplication($a, $b) {
$this->c = $a * $b;
return $this->c;
}
function division($a, $b) {
$this->c = $a / $b;
return $this->c;
}
}
$cc = new calculator;
echo $cc->addition(20, 10)."<br>";
echo $cc->subtraction(20, 10)."<br>";
echo $cc->multiplication(20, 10)."<br>";
echo $cc->division(20, 10)."<br>";
?>
Fasoro Oladipo <dipofasoro at yahoo dot co dot uk>
14-Mar-2004 05:49
<?php
class user {
var $dbconn
function user() {
$this->dbconn = DB::getInformix();
}
function Login($uname, $pass) {
}
function Register($uname, $pass, $name, $email) {
}
function FeedBack($name, $email, $msg) {
}
function Update($name, $email) {
}
function UnRegister() {
}
}
class template {
function showlogin() {
}
function showwelcome() {
}
}
class DB {
function getInformix() {
}
function getMySQL() {
}
function getPostGRESQL() {
}
}
$usr = new user();
$usr->Login($_POST["uname"], $_POST["pass"]);
$usr->Register($_POST["uname"], $_POST["pass"], $_POST["name"], $_POST["email"]);
Login($uname, $pass, $rememberIP);
$usr->Login($_POST["uname"], $_POST["pass"], isset($_POST["remeberIP"]);
?>
heleon
12-Jan-2004 10:22
Hi again,
...to get around the undeclared properties problem is to use Get/Set-functions. The way it should be, and has to be in PHP to be secure.
Heleon
heleon@ergens
12-Jan-2004 10:11
Hi,
Take care with setting properties outside a class. I thought I had extended a var named Name en used it outside its class. After some searching I found that it was not the extended Name that was set but a new generated one. Created when setting it. With normal variables I don't find undeclared vars a problem. But with classes it could get messy I think.
$this->Characters[$this->CharacterID]->Name = "Hank";
Heleon
ar at 5mm de
28-Aug-2003 02:59
I missed some kind of function to dynamicly override or extend an Object:
-----------------------------------------
function &extendObj(&$obj, $code) {
static $num = 0;
$classname = get_class($obj);
$newclass = $classname.$num;
eval('class '.$newclass.' extends '.$classname.' { '.$code.' }');
$newobj = new $newclass();
$vars = get_class_vars($classname);
foreach($vars AS $key=>$value) {
$newobj->$key = &$obj->$key;
}
return $newobj;
}
-----------------------------------------
This creates a new class which extends the old one by the given code parameter, instanciates it and copy all vars from the old obj to the new one.
-----------------------------------------
class testA {
var $prop = 'a';
function funcA($val) {
$this->prop = $val;
}
function value() {
return $this->prop;
}
}
$obj = new testA();
$newobj = &extendObj(&$obj, 'function addX() { $this->prop .= "x"; }');
$newobj->funcA('abc');
$newobj->addX();
echo $newobj->value();
-----------------------------------------
Results in 'abcx'. You can use the function multiple times and also with class variables. Be carefull, even if $newobj is just a copy of $obj, $obj->value() will return 'abcx', too, because of the & operator: $newobj->$key = &$obj->$key;
pixellent at stodge dot net
19-Aug-2003 06:07
In case you were wondering, you can't do the following in PHP:
$name = wsConfig::GetInstance()->GetValue("name");
It causes a parse error, I think due to trying to call GetValue. And yes I do have a function called GetValue in my wsConfig class.
This is my singleton:
function &GetInstance()
{
static $Instance;
if (!isset($Instance))
{
$Instance = new wsConfig();
}
return $Instance;
}
zidsu at hotmail dot com
08-Jul-2003 12:24
FYI: if you want to split your class into manageble chunks, what means different files for you, you can put you functoins into includes, and make include() have a return value. Like this:
class Some_class {
var $value = 3;
function add_value ($input_param) {
return include ("path/some_file.php");
}
}
And your included file:
$input_param += $this->value;
return $input_param;
Then your function call will be:
$instance = new Some_class ();
$instance->add_value (3);
And this will return
6
hopefully :P
Keep in mind though, that the scope in the included file will be identical to the scope the function 'add_value' has.
And if you want to return the outcome, you should also have a return statement made in your include as well.
ninja (a : t) thinkninja (d : o : t) com
10-May-2003 06:37
the best way i found to call an instance of a class from within another class is like so:
class foo {
var $meta = 1;
}
class bar {
var $foo;
function bar(&$objref) //constructor
{
$this->foo =& $objref;
}
function doohickey()
{
return $this->foo->meta;
}
}
$fooclass = new foo();
$barclass = new bar($fooclass);
echo $barclass->doohickey();
asommer*at*as-media.com
20-Sep-2002 09:52
Something I found out just now that comes in very handy for my current project:
it is possible to have a class override itself in any method ( including the constructor ) like this:
class a {
..function ha ( ) {
....if ( $some_expr ) {
......$this = new b;
......return $this->ha ( );
....}
....return $something;
..}
}
in this case assuming that class b is already defined and also has the method ha ( )
note that the code after the statement to override itself is still executed but now applies to the new class
i did not find any information about this behaviour anywhere, so i have no clue wether this is supposed to be like this and if it might change... but it opens a few possibilities in flexible scripting!!
einhverfr at not-this-host dot hotmail dot com
14-Sep-2002 07:35
You may find it helpful in complex projects to have namespaces for your classes, and arrange these in a hierarchical manner. A simple way to do this is to use the filesystem to order your hierarchies and then define a function like this:
function use_namespace($namespace){
require_once("namespaces/$namespace.obj.php");
}
(lack of indentation due to HTML UI for this page)
This requires that all your object libraries end in .obj.php (which I use) but you can modfy it to suit your needs. To call it you could, for exmaple call:
use_namespace("example");
or if foo is part of example you can call:
use_namespace("example/foo");
justin at quadmyre dot com
19-Aug-2002 04:38
If you want to be able to call an instance of a class from within another class, all you need to do is store a reference to the external class as a property of the local class (can use the constructor to pass this to the class), then call the external method like this:
$this->classref->memberfunction($vars);
or if the double '->' is too freaky for you, how about:
$ref=&$this->classref;
$ref->memberfunction($vars);
This is handy if you write something like a general SQL class that you want member functions in other classes to be able to use, but want to keep namespaces separate. Hope that helps someone.
Justin
Example:
<?php
class class1 {
function test($var) {
$result = $var + 2;
return $result;
}
}
class class2{
var $ref_to_class=''; function class1(&$ref){ $this->ref_to_class=$ref; }
function test2($var){
$val = $this->ref_to_class->test($var); return $val;
}
}
$obj1=new class1;
$obj2=new class2($obj1);
$var=5;
$result=obj2->test2($var);
echo ($result);
?>
matthew at fireflydigital dot com
29-Apr-2002 04:48
This is a pretty basic data structure, I know, but I come from a C++ background where these things were "da bomb" when I was first learning to implement them. Below is a class implementation for a queue (first-in-first-out) data structure that I used in a recent project at my workplace. I believe it should work for any type of data that's passed to it, as I used mySQL result objects and was able to pass the object from one page to another as a form element.
# queue.php
# Define the queue class
class queue
{
# Initialize class variables
var $queueData = array();
var $currentItem = 0;
var $lastItem = 0;
# This function adds an item to the end of the queue
function enqueue($object)
{
# Increment the last item counter
$this->lastItem = count($this->queueData);
# Add the item to the end of the queue
$this->queueData[$this->lastItem] = $object;
}
# This function removes an item from the front of the queue
function dequeue()
{
# If the queue is not empty...
if(! $this->is_empty())
{
# Get the object at the front of the queue
$object = $this->queueData[$this->currentItem];
# Remove the object at the front of the queue
unset($this->queueData[$this->currentItem]);
# Increment the current item counter
$this->currentItem++;
# Return the object
return $object;
}
# If the queue is empty...
else
{
# Return a null value
return null;
}
}
# This function specifies whether or not the queue is empty
function is_empty()
{
# If the queue is empty...
if($this->currentItem > $this->lastItem)
# Return a value of true
return true;
# If the queue is not empty...
else
# Return a value of false
return false;
}
}
?>
# Examples of the use of the class
# Make sure to include the file defining the class
include("queue.php");
# Create a new instance of the queue object
$q = new queue;
# Get data from a mySQL table
$query = "SELECT * FROM " . TABLE_NAME;
$result = mysql_query($query);
# For each row in the resulting recordset...
while($row = mysql_fetch_object($result))
{
# Enqueue the row
$q->enqueue($row);
}
# Convert the queue object to a byte stream for data transport
$queueData = ereg_replace("\"", """, serialize($q));
# Convert the queue from a byte stream back to an object
$q = unserialize(stripslashes($queueData));
# For each item in the queue...
while(! $q->is_empty())
{
# Dequeue an item from the queue
$row = $q->dequeue();
}
c.bolten AT grafiknews DOT de
22-Apr-2002 01:14
another way to dynamically load your classes:
==========================
function loadlib($libname) {
$filename = "inc/".$libname.".inc.php";
// check if file exists...
if (file_exists($filename)) {
// load library
require($filename);
return TRUE;
}
else {
// print error!
die ("Could not load library $libname.\n");
}
}
:)
have phun!
-cornelius
a2zofciv2 at hotmail dot com
29-Sep-2001 05:10
I spent 20 minutes or so trying to figure this out, maybe someone else has the same problem.
To access a class' function from within the class you would have to say $this->functionname(params), rather than just functionname(params) like in other programming languages.
Hope this helps
kevin at gambitdesign dot com
04-Jun-2001 09:27
i came across an error something to the extent:
Fatal error: The script tried to execute a method or access a property of an incomplete object.
This was because I had included the file defining the class when i created the object but not in the script when i was trying to access the object as a member variable of a different object
gateschris at yahoo dot com
08-Mar-2001 09:59
[Editor's note: If you are trying to do overriding, then you can just interrogate (perhaps in the method itself) about what class (get_class()) the object belongs to, or if it is a subclass of a particular root class.
You can alway refer to the parent overriden method, see the "Classes and Objects" page of the manual and comments/editor's notes therein.]
There is no function to determine if a member belongs to a base class or current class eg:
class foo {
function foo () { }
function a () { }
}
class bar extends foo {
function bar () { }
function a () { }
}
lala = new Bar();
------------------
how do we find programmatically if member a now belongs to class Bar or Foo.
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variant_xor
