The Basics
class
Every class definition begins with the keyword class, followed by a class name, followed by a pair of curly braces which enclose the definitions of the class's properties and methods.
The class name can be any valid label which is a not a PHP reserved word. A valid class name starts with a letter or underscore, followed by any number of letters, numbers, or underscores. As a regular expression, it would be expressed thus: [a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*.
A class may contain its own constants, variables (called "properties"), and functions (called "methods").
Example #1 Simple Class definition
class SimpleClass
{
// property declaration
public $var = 'a default value';
// method declaration
public function displayVar() {
echo $this->var;
}
}
?> The pseudo-variable $this is available when a method is called from within an object context. $this is a reference to the calling object (usually the object to which the method belongs, but possibly another object, if the method is called statically from the context of a secondary object).
Example #2 Some examples of the $this pseudo-variable
class A
{
function foo()
{
if (isset($this)) {
echo '$this is defined (';
echo get_class($this);
echo ")\n";
} else {
echo "\$this is not defined.\n";
}
}
}
class B
{
function bar()
{
// Note: the next line will issue a warning if E_STRICT is enabled.
A::foo();
}
}
$a = new A();
$a->foo();
// Note: the next line will issue a warning if E_STRICT is enabled.
A::foo();
$b = new B();
$b->bar();
// Note: the next line will issue a warning if E_STRICT is enabled.
B::bar();
?> The above example will output:
$this is defined (A)
$this is not defined.
$this is defined (B)
$this is not defined.
new
To create an instance of a class, a new object must be created and assigned to a variable. An object will always be assigned when creating a new object unless the object has a constructor defined that throws an exception on error. Classes should be defined before instantiation (and in some cases this is a requirement).
Example #3 Creating an instance
$instance = new SimpleClass();
// This can also be done with a variable:
$className = 'Foo';
$instance = new $className(); // Foo()
?> In the class context, it is possible to create a new object by new self and new parent.
When assigning an already created instance of a class to a new variable, the new variable will access the same instance as the object that was assigned. This behaviour is the same when passing instances to a function. A copy of an already created object can be made by cloning it.
Example #4 Object Assignment
$assigned = $instance;
$reference =& $instance;
$instance->var = '$assigned will have this value';
$instance = null; // $instance and $reference become null
var_dump($instance);
var_dump($reference);
var_dump($assigned);
?> The above example will output:
NULL
NULL
object(SimpleClass)#1 (1) {
["var"]=>
string(30) "$assigned will have this value"
}
extends
A class can inherit the methods and properties of another class by using the keyword extends in the class declaration. It is not possible to extend multiple classes; a class can only inherit from one base class.
The inherited methods and properties can be overridden by redeclaring them with the same name defined in the parent class. However, if the parent class has defined a method as final, that method may not be overridden. It is possible to access the overridden methods or static properties by referencing them with parent::
Example #5 Simple Class Inheritance
class ExtendClass extends SimpleClass
{
// Redefine the parent method
function displayVar()
{
echo "Extending class\n";
parent::displayVar();
}
}
$extended = new ExtendClass();
$extended->displayVar();
?> The above example will output:
Extending class
a default value
Properties
" width="11" height="7"> 
Introduction
Last updated: Fri, 25 Sep 2009
" width="11" height="7"> Introduction Last updated: Fri, 25 Sep 2009
add a note User Contributed NotesThe Basics
moty66 at gmail dot com
16-Aug-2009 02:59
16-Aug-2009 02:59
I hope that this will help to understand how to work with static variables inside a class
class a {
public static $foo = 'I am foo';
public $bar = 'I am bar';
public static function getFoo() { echo self::$foo; }
public static function setFoo() { self::$foo = 'I am a new foo'; }
public function getBar() { echo $this->bar; }
}
$ob = new a();
a::getFoo(); // output: I am foo
$ob->getFoo(); // output: I am foo
//a::getBar(); // fatal error: using $this not in object context
$ob->getBar(); // output: I am bar
// If you keep $bar non static this will work
// but if bar was static, then var_dump($this->bar) will output null
// unset($ob);
a::setFoo(); // The same effect as if you called $ob->setFoo(); because $foo is static
$ob = new a(); // This will have no effects on $foo
$ob->getFoo(); // output: I am a new foo
?>
Regards
Motaz Abuthiab alex c
07-Aug-2009 07:17
07-Aug-2009 07:17
ok this really basic but I always forget this. I always get an error like:
Fatal error: Call to a member function on a non-object
when i deal with oops
if it were me finding the error i'd search the internet for hours and then it would occur to me, I'm putting my class operator inside a function, but i would define the class in global file.
so like this:
test.php
include(class.php);
$class = new newclassname;
function function1(){
$class->dofunc();
}
?>
you'll get some die errors and try and do this with function1,
function function1(){
newclassname::dofunc();
}
but if you're using $this inside your class then you'll get another error on non object
so basically, all you need to do is:
function function1(){
$class = new newclassname;
$class->dofunc();
}
or
function function1(){
global $class;
$class->dofunc();
}
i know it's simple, but it always gets me! the_french_cow at hotmail dot com
14-Jul-2009 01:54
14-Jul-2009 01:54
For those of us who are new to inheritance, private functions are not visible in an inherited class. Consider:
class A {
protected function func1() {
echo("I'm func1 in A!
");
}
private function func2() {
echo("I'm func2 in A!
");
}
}
class B extends A {
public function func3() {
echo("I'm func3 in B!
");
$this->func1();
$this->func2(); // Call to private function from extended class results in a fatal error
}
}
$b = new B;
$b->func3(); // Ends in a fatal error
// OR
$b->func1(); // Call to protected function from outside world results in a fatal error
?>
If you want a function to be accessible in class B but not to the outside world, it must be declared as protected. Notes on stdClass
09-Jul-2009 10:26
09-Jul-2009 10:26
stdClass is the default PHP object. stdClass has no properties, methods or parent. It does not support magic methods, and implements no interfaces.
When you cast a scalar or array as Object, you get an instance of stdClass. You can use stdClass whenever you need a generic object instance.
// ways of creating stdClass instances
$x = new stdClass;
$y = (object) null; // same as above
$z = (object) 'a'; // creates property 'scalar' = 'a'
$a = (object) array('property1' => 1, 'property2' => 'b');
?>
stdClass is NOT a base class! PHP classes do not automatically inherit from any class. All classes are standalone, unless they explicitly extend another class. PHP differs from many object-oriented languages in this respect.
// CTest does not derive from stdClass
class CTest {
public $property1;
}
$t = new CTest;
var_dump($t instanceof stdClass); // false
var_dump(is_subclass_of($t, 'stdClass')); // false
echo get_class($t) . "\n"; // 'CTest'
echo get_parent_class($t) . "\n"; // false (no parent)
?>
You cannot define a class named 'stdClass' in your code. That name is already used by the system. You can define a class named 'Object'.
You could define a class that extends stdClass, but you would get no benefit, as stdClass does nothing.
(tested on PHP 5.2.8) webmaster at oehoeboeroe dot nl
04-May-2009 12:03
04-May-2009 12:03
If you pass $this by reference and then assign a new value to it, it will not behave as you might expect as illustrated by this example:
class TestClass
{
public $data;
function setData(&$data) {
$this->data =& $data;
}
function hasData(&$data) {
$saved = $data;
$data = true;
$result = $this->data === true;
$data = $saved;
return $result;
}
function isDataOf(&$object) {
return $object->hasData($this);
}
}
$o1 = new TestClass;
$o2 = new TestClass;
$o1->setData($o2);
$o2->setData($o1);
var_dump($o1->hasData($o2)); // true as expected
var_dump($o2->hasData($o1)); // true as expected
var_dump($o1->isDataOf($o2)); // false even though $o1 is in fact the data of $o2
var_dump($o2->isDataOf($o1)); // false even though $o2 is in fact the data of $o1
?>
You can make this example work by replacing the hasData method with:
function hasData(&$data) {
return $data === $this->data;
}
?>
However, although I've not tested this, I've been told that Zend Engine 1, i.e. PHP 4, will choke on the === parameter when comparing recursing objects. ialsoagree
24-Apr-2009 03:03
24-Apr-2009 03:03
Unfortunately, Arpit's solution creates a new class and leaves the old class inaccessible. If you need access to members of the class you are in you'll be unable to get such access. This can be a huge problem.
However, there is a solution:
class MyClass {
public $message = 'Hello';
public function MyClassFunction() {
function innerFunction(&$this_thing, $message = null) {
$this_thing->message = (!is_null($message)) ? $message : $this_thing->message;
$this_thing->echo_something();
}
innerFunction($this); // echoes 'Hello'
innerFunction($this, '
New Message'); // echoes '
New Message'
}
public function echo_something() {
echo $this->message;
}
}
$class = new MyClass;
$class->MyClassFunction();
?>
By passing $this as a variable by reference, you can access members of the class and even update them. If you don't want to be able to update them, you can simply pass $this to the function but not as a reference. Arpit
06-Feb-2009 02:14
06-Feb-2009 02:14
//try this code if you define a new class inside an object method than we can refer to "$class->message"
//unset this instance doesn't affected the previous one
//it will not report a fatal error
class MyClass {
public $message = 'Hello';
public function MyClassFunction() {
function InnerFunction() {
$class = new MyClass;
print_r($class);
echo $class->message;
unset($class);//unset this doesn't affected the previous one or we can also use different name $classNew=new MyClass;
}
innerFunction();
}
}
$class = new MyClass;
$class->MyClassFunction();
?> ialsoagree
03-Feb-2009 12:23
03-Feb-2009 12:23
I think it's worth mentioning that if you define a function inside of an object method, that function cannot refer to "$this" - doing so will result in PHP reporting a fatal error:
Fatal error: Using $this when not in object context
class MyClass {
public $message = 'Hello';
public function MyClassFunction() {
function InnerFunction() {
echo $this->message; // Reports a fatal error
}
innerFunction();
}
}
$class = new MyClass;
$class->MyClassFunction();
?>
This issue cannot be solved by using the Scope Resolution Operator if you're trying to access a variable:
class MyClass {
public $message = 'Hello';
public function MyClassFunction() {
function InnerFunction() {
echo MyClass::message; // Reports a fatal error
}
innerFunction();
}
}
$class = new MyClass;
$class->MyClassFunction();
?>
Additionally, you can NOT create a public function to access that variable:
class MyClass {
public $message = 'Hello';
public function MyClassFunction() {
function InnerFunction() {
MyClass::echoSomething();
}
innerFunction();
}
public function echoSomething() {
echo $this->message; // Reports a fatal error
}
}
$class = new MyClass;
$class->MyClassFunction();
?>
Note that in this last case, the error is generated on the line below echoSomething function declaration, not at MyClass::echoSomething();
However, it is worth noting that when called directly, echoSomething works fine:
class MyClass {
public $message = 'Hello';
public function MyClassFunction() {
function InnerFunction() {
MyClass::echoSomething();
}
innerFunction();
}
public function echoSomething() {
echo $this->message; // Echoes 'Hello'
}
}
$class = new MyClass;
$class->echoSomething();
?> hugo (@) apres (dot) net
17-Jan-2009 04:37
17-Jan-2009 04:37
A simple approach to Multiple Inheritance
You can give yourself something approaching multiple inheritance with the following class:
class inheritance{
var $bases = array();
static function error_die( $errno, $errstr, $errfile, $errline ) {
$backtrace = debug_backtrace();
$detail = $backtrace[4];
var_dump( $backtrace );
echo 'Fatal Error: '.$errstr.' of class '.$detail["class"].' in '.$detail["file"].' on line '.$detail["line"].'
';
die();
}
private function fatal( $text ) {
set_error_handler( array( 'inheritance', 'error_die' ) );
trigger_error( $text, E_USER_ERROR );
restore_error_handler();
}
function __call( $name, $args ) {
if( $this->bases )
foreach( $this->bases as $base )
if( method_exists( $base, $name ) )
return $base->$name( $args );
$this->fatal( "Call to undefined method ".$name."" );
}
function __set( $name, $value ) {
if( $this->bases )
foreach( $this->bases as $base )
if( property_exists( $base, $name ) ) {
$base->$name = $value;
return;
}
}
function __get( $name ) {
if( $this->bases )
foreach( $this->bases as $base )
if( property_exists( $base, $name ) )
return $base->$name;
}
function __isset( $name ) {
if( $this->bases )
foreach( $this->bases as $base )
if( property_exists( $base, $name ) )
return isset( $base->$name );
}
function __unset( $name ) {
if( $this->bases )
foreach( $this->bases as $base )
if( property_exists( $base, $name ) ) {
unset( $base->$name );
return;
}
}
function inherits( $name, $args = '' ) {
return array_unshift( $this->bases, new $name( $args ) );
}
}
?>
Most of the qualities of multiple inheritance provided by this class are revealed by the following code:
//test inheritance
class base0 {
public $base0var;
public $basevar;
function base0declare() {
echo 'I am base 0';
}
function basedeclare() {
self::base0declare() {
}
}
class base1 extends base0 { // simple linear inheritance here
public $base1var;
public $basevar;
function based1declare() {
echo 'I am base 1';
}
function basedeclare() {
self::base1declare()
}
}
class base2
public $base2var;
public $basevar;
function based2declare() {
echo 'I am base 2';
}
function basedeclare() {
self::base2declare
}
}
?>
Multiple inheritance is achieved by extending the inheritance class, and then in the __construct function placing calls to the "inherits" method of the inheritance class. Each call pushes an instance of the inherited class into an array var which functions as a LIFO stack. Using the magic methods, any failed method call, property set, get, isset or unset is intercepted by the inheritance base class which then attempts to resolve the reference. Object method name conflicts are resolved simply by the later inheritance masking the scope of the earlier inherited method. I recognize there are shortcomings to the approach I offer here, but it works for all my current multiple inheritance needs and offers simplicity and ease of understanding as benefits.
class base_test extends inheritance { // multiple inheritance
function __construct() {
$this->inherits( 'base1' );
$this->inherits( 'base2' );
}
} ?>
Here are some code fragments you can try out to test things.
$testobj = new base_test();
var_dump( $testobj );
$testobj->base2declare();
$testobj->base1declare();
$testobj->base0declare();
$testobj->basedeclare();
$testobj->base2var = 27;
echo $testobj->base2var;
?>
I'd be interested in hearing any comments. chris (@) xeneco (dot) co (dot) uk
27-Nov-2008 11:25
27-Nov-2008 11:25
Regarding object inheritance:
I hope this helps someone, it should help if you're new to OOPS
class A {
public $x = 'A';
public function foo() {
$b = new B;
$b->bar();
return $this->x;
}
}
class B extends A {
public function bar() {
$this->x = 'B';
}
}
$a = new A
echo $a->foo(); //A
?>
I was doing something similar to this (example is greatly simplified to show logic) and spent a long while trying to work out why I would always get 'A' and never get 'B'. Now, after a few weeks, I have revisited the problem and have worked out why:
The code 'new B' creates a new instance of class B. While class B extends class A, it is a new object and not an extension of the object created by 'new A'
The value of $x is set to 'B' within the object $b, but not in object $a.
If within A::foo(), one was to access $b->x then one would obtain the vale 'B', for example
class C {
public $x = 'C';
public function foo() {
$c = new C;
$c->bar();
$this->x = $c->$x
return $this->x;
}
}
class D extends C {
public function bar() {
$this->x = 'D';
}
}
$c = new C
echo $c->foo(); //D
?> Jeffrey
08-Oct-2008 10:49
08-Oct-2008 10:49
A PHP Class can be used for several things, but at the most basic level, you'll use classes to "organize and deal with like-minded data". Here's what I mean by "organizing like-minded data". First, start with unorganized data.
$customer_name;
$item_name;
$item_price;
$customer_address;
$item_qty;
$item_total;
?>
Now to organize the data into PHP classes:
class Customer {
$name; // same as $customer_name
$address; // same as $customer_address
}
class Item {
$name; // same as $item_name
$price; // same as $item_price
$qty; // same as $item_qty
$total; // same as $item_total
}
?>
Now here's what I mean by "dealing" with the data. Note: The data is already organized, so that in itself makes writing new functions extremely easy.
class Customer {
public $name, $address; // the data for this class...
// function to deal with user-input / validation
// function to build string for output
// function to write -> database
// function to read <- database
// etc, etc
}
class Item {
public $name, $price, $qty, $total; // the data for this class...
// function to calculate total
// function to format numbers
// function to deal with user-input / validation
// function to build string for output
// function to write -> database
// function to read <- database
// etc, etc
}
?>
Imagination that each function you write only calls the bits of data in that class. Some functions may access all the data, while other functions may only access one piece of data. If each function revolves around the data inside, then you have created a good class. wbcarts at juno dot com
21-Aug-2008 01:11
21-Aug-2008 01:11
CLASSES and OBJECTS that represent the "Ideal World"
Wouldn't it be great to get the lawn mowed by saying $son->mowLawn()? Assuming the function mowLawn() is defined, and you have a son that doesn't throw errors, the lawn will be mowed.
In the following example; let objects of type Line3D measure their own length in 3-dimensional space. Why should I or PHP have to provide another method from outside this class to calculate length, when the class itself holds all the neccessary data and has the education to make the calculation for itself?
/*
* Point3D.php
*
* Represents one locaton or position in 3-dimensional space
* using an (x, y, z) coordinate system.
*/
class Point3D
{
public $x;
public $y;
public $z; // the x coordinate of this Point.
/*
* use the x and y variables inherited from Point.php.
*/
public function __construct($xCoord=0, $yCoord=0, $zCoord=0)
{
$this->x = $xCoord;
$this->y = $yCoord;
$this->z = $zCoord;
}
/*
* the (String) representation of this Point as "Point3D(x, y, z)".
*/
public function __toString()
{
return 'Point3D(x=' . $this->x . ', y=' . $this->y . ', z=' . $this->z . ')';
}
}
/*
* Line3D.php
*
* Represents one Line in 3-dimensional space using two Point3D objects.
*/
class Line3D
{
$start;
$end;
public function __construct($xCoord1=0, $yCoord1=0, $zCoord1=0, $xCoord2=1, $yCoord2=1, $zCoord2=1)
{
$this->start = new Point3D($xCoord1, $yCoord1, $zCoord1);
$this->end = new Point3D($xCoord2, $yCoord2, $zCoord2);
}
/*
* calculate the length of this Line in 3-dimensional space.
*/
public function getLength()
{
return sqrt(
pow($this->start->x - $this->end->x, 2) +
pow($this->start->y - $this->end->y, 2) +
pow($this->start->z - $this->end->z, 2)
);
}
/*
* The (String) representation of this Line as "Line3D[start, end, length]".
*/
public function __toString()
{
return 'Line3D[start=' . $this->start .
', end=' . $this->end .
', length=' . $this->getLength() . ']';
}
}
/*
* create and display objects of type Line3D.
*/
echo ''
. (new Line3D()) . "\n";
echo ''
. (new Line3D(0, 0, 0, 100, 100, 0)) . "\n";
echo ''
. (new Line3D(0, 0, 0, 100, 100, 100)) . "\n";
?>
<-- The results look like this -->
Line3D[start=Point3D(x=0, y=0, z=0), end=Point3D(x=1, y=1, z=1), length=1.73205080757]
Line3D[start=Point3D(x=0, y=0, z=0), end=Point3D(x=100, y=100, z=0), length=141.421356237]
Line3D[start=Point3D(x=0, y=0, z=0), end=Point3D(x=100, y=100, z=100), length=173.205080757]
My absolute favorite thing about OOP is that "good" objects keep themselves in check. I mean really, it's the exact same thing in reality... like, if you hire a plumber to fix your kitchen sink, wouldn't you expect him to figure out the best plan of attack? Wouldn't he dislike the fact that you want to control the whole job? Wouldn't you expect him to not give you additional problems? And for god's sake, it is too much to ask that he cleans up before he leaves?
I say, design your classes well, so they can do their jobs uninterrupted... who like bad news? And, if your classes and objects are well defined, educated, and have all the necessary data to work on (like the examples above do), you won't have to micro-manage the whole program from outside of the class. In other words... create an object, and LET IT RIP! ashraf dot samhouri at hotmail dot com
24-May-2008 01:35
24-May-2008 01:35
@info -- 20-April
This is because you requested class "b" before defining it, not because you defined class "b" before "a". It doesn't make a difference which class you define first. info at youwanttoremovethisvakantiebaas dot nl
20-Apr-2008 10:40
20-Apr-2008 10:40
if you do this
$x = new b();
class b extends a {}
class a { }
?>
PHP will tell you "class b not found", because you've defined class b before a. However, the error tells you something different.... Got me a little confused :) david dot schueler at tel-billig dot de
15-Feb-2008 02:16
15-Feb-2008 02:16
If you just want to create a new object that extends another object and you want to copy all variables from the father object, you may use this piece of code:
$father =& new father();
$father->a_var = "Hello World.";
$son = new son($event);
$son->say_hello();
class father {
public $a_var;
}
class son extends father {
public function __construct($father_class) {
foreach ($father_class as $variable=>$value) {
$this->$variable = $value;
}
}
public function say_hello() {
echo "Son says: ".$this->a_var;
}
}
?>
This outputs:
Son says: Hello World.
So you dont have to clone the entire object to get the contents of the variables from the father object. aaron at thatone dot com
16-Dec-2007 02:46
16-Dec-2007 02:46
I was confused at first about object assignment, because it's not quite the same as normal assignment or assignment by reference. But I think I've figured out what's going on.
First, think of variables in PHP as data slots. Each one is a name that points to a data slot that can hold a value that is one of the basic data types: a number, a string, a boolean, etc. When you create a reference, you are making a second name that points at the same data slot. When you assign one variable to another, you are copying the contents of one data slot to another data slot.
Now, the trick is that object instances are not like the basic data types. They cannot be held in the data slots directly. Instead, an object's "handle" goes in the data slot. This is an identifier that points at one particular instance of an obect. So, the object handle, although not directly visible to the programmer, is one of the basic datatypes.
What makes this tricky is that when you take a variable which holds an object handle, and you assign it to another variable, that other variable gets a copy of the same object handle. This means that both variables can change the state of the same object instance. But they are not references, so if one of the variables is assigned a new value, it does not affect the other variable.
// Assignment of an object
Class Object{
public $foo="bar";
};
$objectVar = new Object();
$reference =& $objectVar;
$assignment = $objectVar
//
// $objectVar --->+---------+
// |(handle1)----+
// $reference --->+---------+ |
// |
// +---------+ |
// $assignment -->|(handle1)----+
// +---------+ |
// |
// v
// Object(1):foo="bar"
//
?>
$assignment has a different data slot from $objectVar, but its data slot holds a handle to the same object. This makes it behave in some ways like a reference. If you use the variable $objectVar to change the state of the Object instance, those changes also show up under $assignment, because it is pointing at that same Object instance.
$objectVar->foo = "qux";
print_r( $objectVar );
print_r( $reference );
print_r( $assignment );
//
// $objectVar --->+---------+
// |(handle1)----+
// $reference --->+---------+ |
// |
// +---------+ |
// $assignment -->|(handle1)----+
// +---------+ |
// |
// v
// Object(1):foo="qux"
//
?>
But it is not exactly the same as a reference. If you null out $objectVar, you replace the handle in its data slot with NULL. This means that $reference, which points at the same data slot, will also be NULL. But $assignment, which is a different data slot, will still hold its copy of the handle to the Object instance, so it will not be NULL.
$objectVar = null;
print_r($objectVar);
print_r($reference);
print_r($assignment);
//
// $objectVar --->+---------+
// | NULL |
// $reference --->+---------+
//
// +---------+
// $assignment -->|(handle1)----+
// +---------+ |
// |
// v
// Object(1):foo="qux"
?> alan at alan-ng dot net
10-Oct-2007 04:41
10-Oct-2007 04:41
The following odd behavior happens in php version 5.1.4 (and presumably some other versions) that does not happen in php version 5.2.1 (and possibly other versions > 5.1.4).
$_SESSION['instance']=...;
$instance=new SomeClass;
?>
The second line will not only create the $instance object successfully, it will also modify the value of $_SESSION['instance']!
The workaround I arrived at, after trial and error, was to avoid using object names which match a $_SESSION array key.
This is not intended to be a bug report, since it was apparently fixed by version 5.2.1, so it's just a workaround suggestion. mep_eisen at web dot de
10-Aug-2007 01:06
10-Aug-2007 01:06
referring to steven's post:
****
Perhaps this is because =& statements join the 2 variable names in the symbol table, whereas = statements applied to objects simply create a new independent entry in the symbol table that simply points to the same location as other entries. I don't know for sure - I don't think this behavior is documented in the PHP manual, so perhaps somebody with more knowledge of PHP's internals can clarify what is going on.
****
lets talk about
a =& b;
b = c;
PHP internally marks a to be a reference to b. If You reassign b PHP does not update a. But if you access a once more PHP looks at the current value of b (now containing c).
Both statements (a=b and a=&b) seem to do the same but they don't. However this changed for objects from PHP4 to PHP5. Where PHP4 needed this operator to avoid object cloning, PHP5 does not need it.
It is explained in chapter 21 (References Explained). It's important to understand that a becomes a reference and the following code will not modify b:
a =& b;
a =& c; Dan Dascalescu
27-Oct-2006 06:00
27-Oct-2006 06:00
If E_STRICT is enabled, the first example will generate the following error (and a few others akin to it):
Non-static method A::foo() should not be called statically on line 26
The example should have explicitly declared the methods foo() and bar() as static:
class A
{
static function foo()
{
...
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