Web Technology Experts Notes

PHP interview questions and answers for 4 year experience

Question: Difference between include and require?
include: It include a file, It does not find through an warning.
require: It include a file, It does not find through an fatal error, process exit.

Question: How to get IP Address of client?

$_SERVER['REMOTE_ADDR'];

Question: How to get IP Address of Server?

$_SERVER['SERVER_ADDR'];

Question: What is output of following?

$a = '10';
$b = &$a;

$b = "2$b";

echo $a;
echo $b;

Output

210
210

Question: What are the main error types?

Notices: Simple, non-critical errors that are occurred during the script execution.Ideally we should fix all notices.
```
echo $undefinedVar;
```
Warning: more important than Notice but it is also non-critical errors that are occurred during the script execution. It should be fixed.
```
include "non-ExistFile.php";
```
Error: critical errors due to which script execution stopped. It must be fixed.
```
require "non-ExistFile.php";
```

Question: How to enable/disable error reporting?
Enable error

error_reporting(E_ALL);

Disable error

error_reporting(0);

Question: What are Traits?
Traits are a mechanism that allows you to create reusable code in PHP where multiple inheritance is not supported. To create a Traits we use keyword trait.
Example of Traits

trait users {
    function getUserType() { }
    function getUserDescription() {  }
    function getUserDelete() {  }
}

class ezcReflectionMethod extends ReflectionMethod {
    use users;    
}

class ezcReflectionFunction extends ReflectionFunction {
    use users;
}

Question: How to extend a class defined with Final?
No, You can't extend. A class declare with final keyword can't be extend.

Question: What is full form of PSRs?
PHP Standards Recommendations

Question: What is the difference between $message and $$message?
$message is a simple variable whereas $$message is variable whose name is stored in another variable ($message).

Question: How to destroy the session?

session_destroy

Question: How do you execute a PHP script from the command line?

Get the php.exe path from server (My PHP path is : D:\wamp\bin\php\php5.5.12)
In environment variable, Add this path path under PATH variable.
Re-start the computer.
Now, you can execute php files from command file.
```
php hello.php
```

Question: How to repair the session?

REPAIR TABLE tablename

REPAIR TABLE tablename QUICK

REPAIR TABLE tablename EXTENDED

Question: Are Parent constructors called implicitly inside a class constructor?
No, You need to call explicitly.

parent::constructor($value);

Question: What does $_GLOBALS means?
It is associate variable which have all the global data of GET/POST/SESSION/_FILES/ENV/SERVER/GLOBALS etc.

Array
(
    [_GET] => Array
        (
        )

    [_POST] => Array
        (
        )

    [_COOKIE] => Array
        (    
            [_gu] => 1cf7097e-eaf0-486d-aa34-449cf1164ba8
            [_gw] => 2.127103(sc~1,s~oru42c,a~1)127418(sc~1,s~oru42c)u[~0,~0,~0,~0,~0]v[~ev3o1,~4,~0]a()
            [PHPSESSID] => ki18pnad1knttqv5i6233sjem7
        )

    [_FILES] => Array
        (
        )

    [_ENV] => Array
        (
        )

    [_REQUEST] => Array
        (
        )

    [_SERVER] => Array
        (            
            [REQUEST_TIME_FLOAT] => 1501064295.228
            [REQUEST_TIME] => 1501064295
        )

    [GLOBALS] => Array
 *RECURSION*
    [_SESSION] => Array
        (
        )

)

Question: How is it possible to parse a configuration file?

parse_ini_file('config.ini');

Question: What is the difference between characters \034 and \x34? \034 is octal 34 and \x34 is hex 34.

Question: Explain soundex() and metaphone().?
soundex() function calculates the soundex key of a string. A soundex key is a four character long alphanumeric strings that represents English pronunciation of a word.

$str= "hello";
Echo soundex($str);

metaphone() the metaphone() function calculates the metaphone key of a string. A metaphone key represents how a string sounds if pronounced by an English person.

Question: How to start displaying errors in PHP application ? Add following code in PHP.

ini_set('display_errors', 1);
ini_set('display_startup_errors', 1);
error_reporting(E_ALL);

OR
Add following code in .htacess

php_flag display_startup_errors on
php_flag display_errors on
php_flag html_errors on
php_flag  log_errors on

Question: What is stdClass?
It is PHP generic empty class.
stdClass is used to create the new Object. For Example

$newObj = new stdClass();
$newObj->name='What is your name?';
$newObj->description='Tell me about yourself?';
$newObj->areYouInIndia=1;
print_r($newObj);

Output

stdClass Object
(
    [name] => What is your name?
    [description] => Tell me about yourself?
    [areYouInIndia] => 1
)

Question: What is output of below?

$a = '1';
$b = &$a;
$b = "2$b";
echo $a.", ".$b;

output
21, 21

Question:What is the difference between GET and POST?

GET displays the submitted data as part of the URL whereas post does not show.
GET can handle a maximum of 2048 characters, POST has no such restrictions
GET allows only ASCII data, POST has no restrictions, binary data are also allowed.
Normally GET is used to retrieve data while POST to insert and update.

Question:What is traits and give example?
Traits are a mechanism for code reuse in single inheritance languages such as PHP.

class Base {
    public function sayHello() {
        echo 'Hello ';
    }
}

trait SayWorld {
    public function sayHello() {
        parent::sayHello();
        echo 'World!';
    }
}

class MyHelloWorld extends Base {
    use SayWorld;
}

$o = new MyHelloWorld();
$o->sayHello();

output
Hello World

MySQL User defined variables and System variables

Question: What are User-Defined Variables in MySQL?
User-Defined variables are variable that defined by user as per there need. Once they exit from the console, will be removed automatically.

Question: How to set User-Defined Variables in MySQL?

set @name="this is new variable";

Question: How to get User-Defined Variables in MySQL?

select @name;

Question: Can we define multiple variable in single line?
Yes, We can.

set @num1=10, @num2=20, @num3=30;

Question: Can we do arithmetic operators on variable?
Yes, we can do.

select @num1+@num2+@num3; //60
select @num1+@num2+@num3; //6000

Question: Is user defined variable are permanent?
No, It will be removed once close the session.

Question: Can we use user variable with Query?
Yes, If you have defined in same session, then you can use.

Question: What are System Variables?
System Variables explains how your MySQL server are configured and you can change as per your requirement.

Question: How to get the value from system variable?