Create session : session_start();
Set value into session : $_SESSION['USER_ID']=1;
Remove data from a session : unset($_SESSION['USER_ID'];
Set value into session : $_SESSION['USER_ID']=1;
Remove data from a session : unset($_SESSION['USER_ID'];
Saturday, October 24, 2015
What is the difference between Session and Cookie?
What is the difference between Session and Cookie?
The main difference between sessions and cookies is that sessions are stored on the server, and cookies are stored on the user’s computers in the text file format. Cookies can not hold multiple variables,But Session can hold multiple variables.We can set expiry for a cookie,The session only remains active as long as the browser is open.Users do not have access to the data you stored in Session,Since it is stored in the server.Session is mainly used for login/logout purpose while cookies using for user activity tracking
The main difference between sessions and cookies is that sessions are stored on the server, and cookies are stored on the user’s computers in the text file format. Cookies can not hold multiple variables,But Session can hold multiple variables.We can set expiry for a cookie,The session only remains active as long as the browser is open.Users do not have access to the data you stored in Session,Since it is stored in the server.Session is mainly used for login/logout purpose while cookies using for user activity tracking
What's the difference between include and require?
What's the difference between include and require?
If the file is not found by require(), it will cause a fatal error and halt the execution of the script. If the file is not found by include(), a warning will be issued, but execution will continue.
If the file is not found by require(), it will cause a fatal error and halt the execution of the script. If the file is not found by include(), a warning will be issued, but execution will continue.
Write a program to explain how array of objects may be created in java.
public static void main(String[] args) {
Student[] studentArray = new Student[7];
studentArray[0] = new Student();
studentArray[0].marks = 99;
System.out.println(studentArray[0].marks); // prints 99
modify(studentArray[0]);
System.out.println(studentArray[0].marks); // prints 100 & not 99
// code
}
public static void modify(Student s) {
s.marks = 100;
}
Student[] studentArray = new Student[7];
studentArray[0] = new Student();
studentArray[0].marks = 99;
System.out.println(studentArray[0].marks); // prints 99
modify(studentArray[0]);
System.out.println(studentArray[0].marks); // prints 100 & not 99
// code
}
public static void modify(Student s) {
s.marks = 100;
}
Application program and applet program.
An applet is client side program which is downloaded in client side and run in the browser. Applet program can not access network connection like opening socket ,writing to socket. A class extending java.awt.Applet class which has methods like init(), start(), stop(), destroy(),paint() overridden. And cannnot write to client side files i.e. hard disk.
An application runs standalone with a support of virtual machine. An application does not have nay restrictions as Applets have over network and file related activities.They are free to open sockets over a network read and write to a file.
An application runs standalone with a support of virtual machine. An application does not have nay restrictions as Applets have over network and file related activities.They are free to open sockets over a network read and write to a file.
What is abstract class? Explain need of abstract class with example.
Abstract classes are classes that contain one or more abstract methods. An abstract method is a method that is declared, but contains no implementation. Abstract classes may not be instantiated, and require subclasses to provide implementations for the abstract methods. Let's look at an example of an abstract class, and an abstract method.
abstract class Bike{
abstract void run();
}
abstract void run();
}
class Honda extends Bike{
void run(){System.out.println("Honda is a good bike..");}
void run(){System.out.println("Honda is a good bike..");}
public static void main(String args[]){
Bike obj = new Honda();
obj.run();
}
}
Bike obj = new Honda();
obj.run();
}
}
What is rule of accessibility at java?
We can have all the four access modifiers for class member variables and methods. However member access modifier rules get applied after the class level access rules. For example, if class is having default access, then it will not be visible in other packages and hence methods and variables of the class will also be not visible.
public keyword
If class member is “public” then it can be accessed from anywhere. The member variable or method is accessed globally. This is simplest way to provide access to class members, however we should take care in using this keyword with class variables otherwise anybody can change the values. Usually class variables are kept as private and getter-setter methods are provided to work with them.
private keyword
If class member is “private” then it will be accessible only inside the same class. This is the most restricted access and the class member will not be visible to the outer world. Usually we keep class variables as private and methods that are intended to be used only inside the class as private.
protected keyword
If class member is “protected” then it will be accessible only to the classes in the same package and to the subclasses. This modifier is less restricted from private but more restricted from public access. Usually we use this keyword to make sure the class variables are accessible only to the subclasses.
public keyword
If class member is “public” then it can be accessed from anywhere. The member variable or method is accessed globally. This is simplest way to provide access to class members, however we should take care in using this keyword with class variables otherwise anybody can change the values. Usually class variables are kept as private and getter-setter methods are provided to work with them.
private keyword
If class member is “private” then it will be accessible only inside the same class. This is the most restricted access and the class member will not be visible to the outer world. Usually we keep class variables as private and methods that are intended to be used only inside the class as private.
protected keyword
If class member is “protected” then it will be accessible only to the classes in the same package and to the subclasses. This modifier is less restricted from private but more restricted from public access. Usually we use this keyword to make sure the class variables are accessible only to the subclasses.
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