[Please Read Introduction
to Classes in C++, Unit
Conversion Program using Classes, A
Multi-Purpose String Class in C++ etc. for more information. Despite
being from C++'s perspective they're useful.]
In PHP a class is defined as following:
class myclass
{
...
...
}
For C/C++ programmers, do note that there’s no ‘;’ after
the closing curly brace.
A variable can be defined inside a class (AKA member variable) as:
class myclass
{
//notice the use of 'var'
var $var;
...
...
}
NOTE: We have to use ‘var’ keyword to define variables.
A function can also be defined inside a class as following. These functions
are known as Member Functions.
class myclass
{
function myfunc()
{
echo "myfunc";
}
...
...
}
Accessing Members
Classes as you might know is just like a user-defined data-type, they don’t
have any useful existence before we create instances or objects of that class.
Objects of a class may be created as:
$ob1=new myclass;
Now that ‘$ob1’ is an object of ‘myclass’ it holds
its copy of the member variables and functions declared in the class that can
be accessed as:
$ob1->var;
And functions as:
$ob1->myfunc();
Consider the following example code:
class myclass
{
var $var;
function myfunc()
{
echo "myfunc";
}
}
$ob1=new myclass;
$ob2=new myclass;
$ob2->var=10;
echo $ob1->var;
$ob1->myfunc();
$ob2->myfunc();
Access Specifiers
You may control the accessibility of member variables and member functions
from outside the class using ‘Access Specifiers’. You have previously
seen that we can access members of a class using the following form:
echo $ob1->var;
And the members were accessible, because that is the default Access Specified
for all the members declared inside a class. So by default members of a class
have been given ‘public’ access from outside the class which can
also optionally be done using the ‘public’ keyword. Other access
specifies include ‘private’ and ‘protected’. Privately
declared members of a class are not accessible from outside the class (using
the ‘->’ method we have discussed). They however are accessible
only to other member functions of the same class. We’ll discuss about
‘protected’ access specifier in future posts as it first requires
‘inheritance’ to be discussed.
The following code illustrates it quite well:
class myclass2
{
//no 'var' keyword
private $var;
function myfunc()
{
echo "myfunc";
$var=2;
// 'var' accessible to Member Function
echo $var;
}
}
$ob1=new myclass2;
//not accessible
echo $ob1->var;
$ob1->myfunc();
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