php interview questions and answers for experienced candidates

What is difference between include,require,include_once and require_once() ?

Include :-Include is used to include files more than once in single PHP script.You can include a file as many times you want.

Syntax:- include(“file_name.php”);

Include Once:-Include once include a file only one time in php script.Second attempt to include is ignored.

Syntax:- include_once(“file_name.php”);

Require:-Require is also used to include files more than once in single PHP script.Require generates a Fatal error and halts the script execution,if file is not found on specified location or path.You can require a file as many time you want in a single script.

Syntax:- require(“file_name.php”);

Require Once :-Require once include a file only one time in php script.Second attempt to include is ignored. Require Once also generates a Fatal error and halts the script execution ,if file is not found on specified location or path.

Syntax:- require_once(“file_name.php”);

 What is cURL in PHP ?

cURL is a library in PHP that allows you to make HTTP requests from the server.

There are so many functions available for displaying output in PHP. The basic functions for displaying output in PHP are as follows:

  • print() Function
  • echo() Function
  • printf() Function
  • sprintf() Function
  • Var_dump() Function
  • print_r() Function
  • Session and cookie both are used to store values or data.
  • cookie stores data in your browser and a session is stored on the server.
  • Session destroys that when browser close and cookie delete when set time expires.

Static Members of a Class can be accessed directly using a class name with a scope resolution operator. To access Static members we don’t need to create an object of Class.

Example

class Hello {
    public static $greeting = 'Greeting from Hello Class';
}

echo Hello::$greeting; // outputs "Greeting from Hello Class"

An access specifier is a code element that is used to determine which part of the program is allowed to access a particular variable or other information. Different programming languages have different syntax to declare access specifiers. There are three types of access specifiers in PHP which are:

  • Private: Members of a class are declared as private and they can be accessed only from that class.
  • Protected: The class members declared as protected can be accessed from that class or from the inherited class.
  • Public: The class members declared as public can be accessed from everywhere.

array_combine is used to combine two or more arrays while array_merge is used to append one array at the end of another array.

array_combine is used to create a new array having keys of one array and values of another array that are combined with each other whereas array_merge is used to create a new array in such a way that values of the second array append at the end of the first array.

array_combine doesn’t override the values of the first array but in array_merge values of the first array overrides with the values of the second one.

Example of array_combine

<?php
$arr1    = array("sub1","sub2","sub3");
$arr2    = array(("php","html","css");
$new_arr = array_combine($arr1, $arr2);
print_r($new_arr);
?>

OUTPUT:

 Array([sub1] => php [sub2] => html [sub3 =>css)

Example of array_merge

<?php
$arr1 = array("sub1" => "node", "sub2" => "sql");
$arr2 = array("s1"=>"jQuery", "s3"=>"xml", "sub4"=>"Css");
$result = array_merge($arr1, $arr2);
 print_r($result);
?>

OUTPUT:

Array ([s1] => jquery [sub2] => sql [s3] => xml [sub4] =>Css )

getimagesize() function is used to get the size of an image in PHP. This function takes the path of file with name as an argument and returns the dimensions of an image with the file type and height/width. Syntax:

array getimagesize( $filename, $image_info )

The mail function is used in PHP to send emails directly from script or website. It takes five parameters as an argument.

Syntax of mail (): mail (to, subject, message, headers, parameters);

Overriding and Overloading both are oops concepts.

In Overriding, a method of the parent class is defined in the child or derived class with the same name and parameters. Overriding comes in inheritance.

An example of Overriding in PHP.

<?php

class A {
   function showName() {
      return "Ajay";
   }
}

class B extends A {
   function showName() {
      return "Anil";
   }
}

$foo = new A;
$bar = new B;
echo($foo->myFoo()); //"Ajay"
echo($bar->myFoo()); //"Anil"
?>

In Overloading, there are multiple methods with the same name with different signatures or parameters. Overloading is done within the same class. Overloading is also called early binding or compile time polymorphism or static binding.

An example of Overloading in PHP

<?php 
class A{

function sum($a,$b){
	return $a+$b;

}

function sum($a,$b,$c){
	return $a+$b+$c;

}

}

$obj= new A;
$obj->sum(1,3); // 4
$obj->sum(1,3,5); // 9
?>

13) What is a composer in PHP?

It is an application-level package manager for PHP. It allows you to declare the libraries your project depends on and it will manage (install/update) them for you.

 

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