Note to the solution by 'zabmilenko at hotmail dot com':
Good idea but encapsulation is a better technique which is also more portable and reliable.
You can pass an object which is based on an interface/superclass to the common DB interface.
For instance:
<?php
class DB_Common {
// data can be either an uri or array depending on how you construct it
// e.g. data = array('host' => 'x.x.x.x', 'port' => '65535', 'etc' => '...')
function connect($data) { die("must be overriden by subclass"); }
function disconnect() { die("..."); }
function query($query) { die("..."); }
}
class DB_MySQL extends DB_Common { /* override methods here */ }
class DB_PgSQL extends DB_Common { /* same here */
class DB_Frontend {
var $errmsg = array('DB_Common subclass-string or object required');
var $_db;
// PHP4/5 compat
function DB_Frontend($arg) { $this->__construct($arg); }
function __construct($arg) {
if( is_object($arg) && is_a($arg, 'DB_Common') )
$this->_db = $arg;
else
{
if( !is_string($arg) )
die($this->errmsg[0]);
$arg = "DB_$arg";
if( !class_exists($arg) )
die($this->errmsg[0]);
$this->_db = new $arg;
// use is_subclass_of(object, string) for compat with older versions
if( !is_subclass_of($arg, 'DB_Common') )
die($this->errmsg[0]);
}
}
// add connect, disconnect that simply calls $this->_db->method() instead
function getOne($quey) {
// preprocess query if needed
$result = $this->_db->query($query);
// process result if needed
return $result;
}
/* add more methods if needed */
}
// string parameter
$frontend = new DB_Frontend('MySQL');
// object parameter
$backend = new DB_MySQL();
$frontend = new DB_Frontend($backend);
?>
You can also use a static DB class. If you see PEAR::DB you will see how all this is quite equal to eachother. The main difference is the frontend class which should encapsulte the backend.
Suggestions and/or comments appreciated.
XII. Classes/Objects 类／对象函数
简介
本类函数允许获取类和对象实例的信息。可以取得对象所属的类的名字，以及它的成员属性和方法。通过使用这些函数，不仅可以弄清楚一个对象类的全体成员，而且可以知道它的起源（例如，该对象类是哪个类的扩展）。
需求
要编译本扩展模块不需要外部库文件。
安装
本函数库作为 PHP 内核的一部分，不用安装就能使用。
运行时配置
本扩展模块在 php.ini 中未定义任何配置选项。
资源类型
本扩展模块未定义任何资源类型。
预定义常量
本扩展模块未定义任何常量。
范例
在本例子中，先定义一个基础类和一个扩展类。基础类描述的是普通的蔬菜（Vegetable），它是否可食用（is_edible）以及它是什么颜色（what_color）。子类 Spinach 增加了“烹调”的方法（cook_it）和“获知它是否已被烹调了”的方法（is_cooked）。
接着，从这些对象中创建两个对象实例，打印出它们的相关信息，包括它们的起源。还定义了一些实用函数，它们主要是为了让变量的输出好看些。
例子 2. test_script.php
上边例子中重点要注意的是对象 $leafy 是 Spinach 类的一个实例，而 Spinach 类是 Vegetable 类的一个子类，因此上边脚本的最后部分将会输出：
|
- 目录
- call_user_method_array -- 调用一个用户方法，同时传递参数数组［已停用］
- call_user_method -- 调用特定对象的用户方法［已停用］
- class_exists -- 检查类是否已定义
- get_class_methods -- 返回由类的方法名组成的数组
- get_class_vars -- 返回由类的默认属性组成的数组
- get_class -- 返回对象的类名
- get_declared_classes -- 返回由已定义类的名字所组成的数组
- get_declared_interfaces -- Returns an array of all declared interfaces
- get_object_vars -- 返回由对象属性组成的关联数组
- get_parent_class -- 返回对象或类的父类名
- interface_exists -- Checks if the interface has been defined
- is_a -- 如果对象属于该类或该类是此对象的父类则返回 TRUE
- is_subclass_of -- 如果此对象是该类的子类，则返回 TRUE
- method_exists -- 检查类的方法是否存在
- property_exists -- Checks if the object or class has a property
add a note
User Contributed Notes
kim dot hermansson at gmail dot com
01-Sep-2006 11:40
01-Sep-2006 11:40
beconfused at googlemail dot com
20-Jul-2006 09:18
20-Jul-2006 09:18
function from Tobias K.....
stdClass Object to XML
xml:
[CODE]
"$xml<?xml version='1.0' standalone='yes'?>" .
"<movies>" .
"<movie eur=\"10.00\">" .
"<title>PHP: Behind the Parser</title>" .
"<characters>" .
"<character>" .
"<name>Ms. Coder</name>" .
"<actor>Onlivia Actora</actor>" .
"</character>" .
"<character>" .
"<name>Mr. Coder</name>" .
"<actor>El Actr</actor>" .
"</character>" .
"</characters>" .
"<plot>" .
"Text bla bla." .
"</plot>" .
"<rating ulf=\"integer\">7</rating>" .
"<rating type=\"stars\">5</rating>" .
"</movie>" .
"</movies>";
[/CODE]
stdObject:
[CODE]
stdClass Object
(
[movie] => stdClass Object
(
[title] => PHP: Behind the Parser
[characters] => stdClass Object
(
[character] => Array
(
[0] => stdClass Object
(
[name] => Ms. Coder
[actor] => Onlivia Actora
)
[1] => stdClass Object
(
[name] => Mr. Coder
[actor] => El Actr
)
)
)
[plot] => Text bla bla.
[rating] => Array
(
[0] => stdClass Object
(
[_] => 7
[ulf] => integer
)
[1] => stdClass Object
(
[_] => 5
[type] => stars
)
)
[eur] => 10
)
)
[/CODE]
Aufruf:
[PHP]
$s = htmlentities(asXML($r,"movies",array(
"movies/movie" => "eur",
"movies/movie/rating" => "ulf type"
)));
[/PHP]
Funktion:
[PHP]
function asXML($obj, $name, $attrNames=NULL, &$xml="", $path="", $depth=0) {
if (is_array($obj)) {
foreach ($obj as $v)
asXML($v,$name,$attrNames,$xml,$path,$depth);
} else {
if ($path) $xml .= "\n";
$path = $path ? "$path/$name" : $name;
$indent = str_repeat(" ",$depth*4);
$xml .= "$indent<$name";
$attr = $attrNames[$path];
if ($attr) {
if (!is_object($obj))
throw new Exception("asXML(): ".
"$path is no object, so it cannot hold attributes");
$attr = explode(" ",$attr);
foreach ($attr as $key)
if ($obj->$key) $xml .= " $key=\"{$obj->$key}\"";
}
$xml .= ">";
if (is_object($obj)) {
$xml .= $obj->_;
$len = strlen($xml);
foreach (get_object_vars($obj) as $key => $value)
if ($key!="_" && (!is_array($attr) || !in_array($key,$attr)))
asXML($value,$key,$attrNames,$xml,$path,$depth+1);
if ($len!=strlen($xml)) $xml .= "\n$indent";
} else {
$xml .= $obj;
}
$xml .= "</$name>";
}
return $xml;
}
[/PHP]
Chris
26-Oct-2005 06:06
26-Oct-2005 06:06
You could reformat your query to use the 'as colname'
<? $db->query("select found_rows() as found_rows"); ?>
pascal dot poncet at netconsult dot com
13-Oct-2005 10:21
13-Oct-2005 10:21
Subject: using "sql_calc_found_rows" in a MySQL query while exploiting result in a PHP db class object.
Hello,
There is a nice function in MySQL that allows to know how many records would have been returned if no "where" clause were set : SQL_CALC_FOUND_ROWS.
If you have create a db object to collect the returned lines, you will be a little perplex when trying to call the result of this function.
Why ?
Simply because the returned field's name is "found_rows()" and obviously it's not possible to call something like :
<?php $result->found_rows() ?>
...as it will try to acces a method, not a property !
Then, the only way to get the right result seems to be the use of a class function, like :
<?php
$db->query("select found_rows()");
$count=current(get_object_vars(current($db->result)));
?>
Of course, if somebody found an other way to solve it, like a special syntax (see the one used with curled arrays in a string), I'm really open to discuss.
Good luck,
Pascal
ia [AT] zoznam [DOT] sk
03-Aug-2005 01:55
03-Aug-2005 01:55
as for zabmilenko's solution:
wouldn't it be better to create it this way?
<?php
// The base class for all db classes
class DB {
protected $connectId;
}
// Class for MySQL, which extends base class
class MySQL extends DB {
function connect () {
$this->connectId = mysql_connect (...);
}
}
// Class for PostgreSQL, which extends base class
class pgSQL extends DB {
function connect () {
$this->connectId = pg_connect (...);
}
}
// and then call constructor like this:
$dbName = "MySQL";
$db = new $dbName ( ... );
// ... which creates an object of class MySQL
?>
zabmilenko at hotmail dot com
27-Jun-2005 03:08
27-Jun-2005 03:08
((PHP5))
I wanted to dynamically choose an extender for a class. This took awhile of playing with it but I came up with a solution. Note that I can't verify how safe it is, but it appears to work for me. Perhaps someone else can shed light on the details:
<?php
class A { var $value = "Class A\n"; }
class B { var $value = "Class B\n"; }
// Uncomment which extender you want. You can use variables as well.
// define('__EXTENDER__', 'A');
define('__EXTENDER__', 'B');
// Use eval to create a wrapper class.
eval('class EXTENDER extends '. __EXTENDER__ . ' { }');
class C extends EXTENDER
{
function __construct()
{
echo $this->value;
}
}
$t = new C;
?>
Outputs: Class B
Practical application: I have a database abstraction system that has individual classes for mysql, pgsql, et al. I want to be able to create a global db class that extends one of the individual db classes depending on the application configuration.
I know that there are probably much better ways of doing this but I haven't reached that level when it comes to classes.
cjones
04-Mar-2005 05:27
04-Mar-2005 05:27
If anyone is interested in looking for a way to dynamically load existing objects into a class, here is what I found very useful.
//---------------------------------------------------------
// Dynamically load External Objects into a class
function objRef ( &$obj ) {
eval("\$this->obj_".get_class($obj)." = \$obj;");
}
//---------------------------------------------------------
// Reference by using: $this->obj_[object Name]->[var|f{}]
Example:
class date { function date ( ) { $this->date = "March 3rd"; } }
class time { function time ( ) { $this->time = "12:30pm"; } }
class show {
function objRef ( &$obj ){
eval("\$this->obj_".get_class($obj)." = \$obj;");
}
function test ( $var ){
echo "$var".$this->obj_date->date." @ ".$this->obj_time->time;
}
}
$date = new date;
$time = new time;
$show = new show;
$show->objRef($date);
$show->objRef($time);
$show->test("Time Now => ");
// Output: Time Now => March 3rd @ 12:30pm
I found the prefix 'obj_' before the class name useful because it helped me to automatically identify external object references when scanning through my scripts. You can omit this if you want. Hope this helps someone.
http://sc.tri-bit.com/ StoneCypher
03-Mar-2005 02:25
03-Mar-2005 02:25
to covertka at muohio dot edu and pillepop2003 at yahoo dot de:
There's a much easier solution to getting a class' name for working with a factory function. Let's assume you're doing something like this:
<?php
function FactoryFunction($whatever, $instancedata) {
switch ($whatever) {
case 'stuff' : return new Stuff($instancedata);
case 'otherstuff' : return new Otherstuff($instancedata);
}
}
?>
Now, consider the named parameter idiom and remember that PHP uses hashes for everything; as a result make the following changes:
<?php
function FactoryFunction($whatever, $instancedata) {
switch ($whatever) {
case 'stuff' : return array('typeis'=>'stuff', 'instance'=>new Stuff($instancedata));
case 'otherstuff' : return array('typeis'=>'otherstuff', 'instance'=>new Otherstuff($instancedata));
}
}
?>
Nice 'n simple. It seems that what the original poster wanted was something like C++ static data members; unfortunately as PHP4 has no static variables at all, there would need to be significant language change to support static-like behavior. If you move to PHP5, the static keyword solves your problem cleanly.
covertka at muohio dot edu
03-Jan-2005 09:27
03-Jan-2005 09:27
To pillepop2003 at yahoo dot de:
I have the same issue. I have a base class that manages database tasks for a number of child classes. One of the functions in the base class is a find() method that returns instances of the child classes. Since find() is usually called as a static method, it needs to know the name of the child class. As you've found, this appears to be impossible to get in an easy fashion.
The only way I've found to get the child class name is to use the debug_traceback() function. This requires me to have a find() method in every child class, but it does work.
Here's an example:
<?php
require_once("Application.php");
class parentClass {
function find() {
$className = NULL;
foreach (debug_backtrace() as $bt) {
if ($bt['function'] == __FUNCTION__) {
$className = $bt['class'];
}
}
// here should be some code to find the proper id, let's assume it was id 1
$id = 1;
return new $className($id);
}
}
class foo extends parentClass {
function __construct($id) {
$this->id = id;
}
function find() {
return parent::find();
}
}
class bar extends parentClass {
function __construct($id) {
$this->id = id;
}
function find() {
return parent::find();
}
}
$a = foo::find();
printf("Type for \$a: %s<br/>\n", get_class($a));
$b = bar::find();
printf("Type for \$b: %s<br/>\n", get_class($b));
?>
iparanoid at gmx dot de
05-Aug-2004 02:17
05-Aug-2004 02:17
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 10:58
06-Jul-2004 10:58
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
19-Jun-2004 07:59
19-Jun-2004 07:59
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 08:46
10-Jun-2004 08:46
// 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 $child;
}
HOC
29-May-2004 12:40
29-May-2004 12:40
to pillepop2003
Why do u want to know the classname of an non-existant object?
The only possible explanation for this question seems to me u want to know the class before u instantiate the object. Well, this is of no use since u always instantiate a class of ur choice.
When the class is instantiated into an object u can find the class of the object by means of get_class(). This is all u need. In case of inheritance u can use get_class($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.
mfirat at fibronline dot com
02-Apr-2004 09:18
02-Apr-2004 09:18
<?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 $cc->division(20, 10)."<br>";
?>
ar at 5mm de
28-Aug-2003 10:59
28-Aug-2003 10:59
I missed some kind of function to dynamicly override or extend an Object:
-----------------------------------------
function &extendObj(&$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;
zidsu at hotmail dot com
08-Jul-2003 08:24
08-Jul-2003 08:24
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.
asommer*at*as-media.com
21-Sep-2002 05:52
21-Sep-2002 05:52
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 $something;
..}
}
in this case assuming that class b is already defined and also has the method ha ( )
note that the code after the statement to override itself is still executed but now applies to the new class
i did not find any information about this behaviour anywhere, so i have no clue wether this is supposed to be like this and if it might change... but it opens a few possibilities in flexible scripting!!
einhverfr at not-this-host dot hotmail dot com
15-Sep-2002 03:35
15-Sep-2002 03:35
You may find it helpful in complex projects to have namespaces for your classes, and arrange these in a hierarchical manner. A simple way to do this is to use the filesystem to order your hierarchies and then define a function like this:
function use_namespace($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
20-Aug-2002 12:38
20-Aug-2002 12:38
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 $ref_to_class=''; # to be pointer to other class
function class1(&$ref){ #constructor
$this->ref_to_class=$ref; #save ref to other class as property of this class
}
function test2($var){
$val = $this->ref_to_class->test($var); #call other class using ref
return $val;
}
}
$obj1=new class1;
# obj1 is instantiated.
$obj2=new class2($obj1);
# pass ref to obj1 when instantiating obj2
$var=5;
$result=obj2->test2($var);
# call method in obj2, which calls method in obj1
echo ($result);
?>
a2zofciv2 at hotmail dot com
29-Sep-2001 01:10
29-Sep-2001 01:10
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
gateschris at yahoo dot com
08-Mar-2001 05:59
08-Mar-2001 05:59
[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.