PHP Interview Question Answer
1 - When Import Data in phpmyadmin then Error show file size exceeded the maximum size permitted by your PHP configuration.

Follow theses steps

Open php.ini file

Search below code

; Maximum allowed size for uploaded files.
upload_max_filesize = 2M

we can change max 8M size here, then restart apache and mysql

2 - what is the difference between include and include_once?

Include We include file many times in single script. Include_once This will include file only one time, second if we include this file this will be ignore

3 - What is encapsulation?

An act of combining properties and methods, related to the same object, is known as encapsulation

4 - What is array_combine()?

array_combine() function create an array by using keys and values. both array must be equal.

<?php
$index=array("A","B","C");
$value=array("50","40","50");
$result=array_combine($index,$value);
print_r($result);
?>

output-
Array ( [A] => 50 [B] => 40 [C] => 50 )

5 - Full Form of PHP Open source softwares

XAMPP stands for Cross-Platform (X), Apache (A), MySQL (M), PHP (P) and Perl (P)
WAMP stands for Windows (W), Apache (A), MySQL (M) and PHP(P)
LAMP stands for Linux (L), Apache (A), MySQL (M) and PHP(P)
MacOS stands for MacOS (M), Apache (A), MySQL (M) and PHP(P)

6 - What is the purpose of php.ini file?

php.ini is a default configuration file require for running application, we edit this as per our requirement
In xampp we can see this file on xampp->php->php.ini

Some php.ini setting we can do.

Increase memory limit
we can enable short tag
we can change max_execution_time
To enable or disable display error,log error,html error, log error ...
We can increase or decrease File uploading size
We can increase or decrease Maximum number of file upload
we can add/remove/comment extension like extension=php_mbstring.dll

7 - What is a Persistent Cookie?

A persistent cookie is permanently stored on Client computer this will create notepad file, But temporary cookie erased when we close broswer.

For Permanent cookie we use set_cookie()

For Temporary cookie we use $_SESSION[]

8 - What are SQL Injections?

SQL Injections are a method to print SQL Statement in browser. Hacker easily get information etc.

9 - What is the difference between == and === operator?

== equal operator is use to check two value is equal or not. If we use === operator then it will check two value is equal with same data type

10 - Mysql Query to Find 2nd hightest salary from the employee table

Query1
SELECT DISTINCT salary FROM emp ORDER by salary desc LIMIT 1,1

Query2
SELECT (salary) FROM emp GROUP BY salary DESC LIMIT 1,1

Query3
SELECT salary FROM emp
WHERE salary = (SELECT (salary) FROM emp GROUP BY salary DESC LIMIT 1,1)

All above these query doing same work.

11 - What does array_count_values?

This function will counts all the values of an array

<?php
$a=array("Sunday","Monday","Sunday","Monday","Tuesday");
print_r(array_count_values($a));
?>

Output:
Array ( [Sunday] => 2 [Monday] => 2 [Tuesday] => 1 )

12 - List data types in PHP ?

integer
boolean
float
string
array
object
callable
resource
NULL

13 - Difference between PHP5 and PHP7

In PHP7 New Spaceship Operator(<=>) Introduce

$a <=> $b;
Same as in PHP5 We use
$a>$b ? 1 : -1

<?php
$x=32;
$y=66;
echo $x>$y ? 1 : -1; //PHP5
echo $x<=>$y; //PHP7
?>

In php 5 we can use mysql_* and mysqli_*, but in php mysql_* functions are completely removed, we use mysqli_* only

asp style tags(<% %>) and script tag(<script language="php"></script>) removed.

Function parameter type and Return type is possible.

14 - Swap two value without using third variable

Code 1

<?php
$a=5;
$b=6;
$a=$a+$b;
$b=$a-$b;
$a=$a-$b;
echo $a;
echo "<br>";
echo $b;
?>

Code 2

<?php
$a=5;
$b=6;
list($a,$b)=array($b,$a);
echo $a;
echo "<br>";
echo $b;
?>

15 - How can we get the IP address of the client?

$_SERVER["REMORTE_ADDR"] Superglobal variable is use to get IP Address

16 - What is the output of the code?

<?php
$x = '71';
$y = &$x;
$y = "2$y";
echo $x;
?>

17 - MySQL storage engines

InnoDB
MyISAM
Memory
CSV
Merge
Archive
Federated
Blackhole
Example

InnoDB is the most widely used storage engine with transaction support.

MyISAM is the original storage engine. It is a fast storage engine. It does not support transactions.

Memory storage engine creates tables in memory. It is the fastest engine.

CSV stores data in CSV files.

Merge operates on underlying MyISAM tables.

Archive storage engine is optimised for high speed inserting. It compresses data as it is inserted

The Blackhole storage engine accepts but does not store data. Retrievals always return an empty set.

Federated storage engine offers the ability to separate MySQL servers to create one logical database from many physical servers.

18 - How to Convert Date to Unix time stamp and Unix time stamp to Date

strtotime()- Convert Date into Unix time stamp

<?php
echo(strtotime("now") . "<br>");
echo(strtotime("13 October 2018") . "<br>");
?>

Date()- Convert Unix time stamp to Date

<?php
$timestamp=1549974080;
echo date("Y-m-d", $timestamp);
?>

19 - How can we define a constant PHP?

define() is use to define constant

Example
define ("Salary",5000);

20 - What is default session time?

24 minutes(1440 seconds)

21 - What is the difference between unset() and unlink()?

unset() is sets a variable to undefined(means variable delete)
unlink() is use to delete file.

22 - How can we remove HTML Tags from Data?

Strip_tags() function


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