PHP Interview Questions and Answers. Latest PHP Interview questions.
Explain to me about PHP?
PHP Stands Hypertext Preprocessor is open-source server-side scripting language that is widely used for web development. Php spcripts are executed on the server. Php allows writing dynamically generated web pages efficiently and quickly. The syntax is mostly borrowed from C, Java and perl. Php is free to download and use.
Echo vs. print
echo() and print() are language constructs in PHP, both are used to output strings. The speed of both statements is almost the same.
echo() can take multiple expressions whereas print cannot take multiple expressions.
Print return true or false based on success or failure whereas echo doesn’t return true or false.
$message vs. $$message in PHP.
$message is a variable with a fixed name. $$message is a variable whose name is stored in $message.
If $message contains “var”, $$message is the same as $var. Ex :
- $x = “Dheeraj”;
- $$x = 4000;
- echo $x.”<br/>”;
- echo $$x.”<br/>”;
- echo $abc;
Output of the code
different types of errors in PHP.
Notices, Warnings and Fatal errors are the types of errors in PHP
Notices represents non-critical errors, i.e. accessing a variable that has not yet been defined. By default, such errors are not displayed to the user at all but whenever required, you can change this default behavior.
Warnings are more serious errors but they do not result in script termination. i.e calling include() a file which does not exist. By default, these errors are displayed to the user.
Fatal errors are critical errors i.e. calling a non-existent function or class. These errors cause the immediate termination of the script
importance of the function htmlentities.
The htmlentities() function converts characters to HTML entities.
What is MIME?
MIME – Multi-purpose Internet Mail Extensions.
MIME types represents a standard way of classifying file types over Internet.
Web servers and browsers have a list of MIME types, which facilitates files transfer of the same type in the same way, irrespective of operating system they are working in.
A MIME type has two parts: a type and a subtype. They are separated by a slash (/).
MIME type for Microsoft Word files is application and the subtype is msword, i.e. application/msword
Explain how to execute a PHP script using the command line.
PHP script using the command line can be executed using SAPI (Server Application Programming Interface). Using SAPI Command Line Interface the PHP code can be passed to execute directly
Php –r ‘print_r(get_defined_constanrs());’
From a shell, php –v will display whether the SAPI is CLI or CGI
| How can we increase the execution time of a PHP script? |
By default, the PHP script takes 30secs to execute. This time is set in the php.ini file. This time can be increased by modifying the max_execution_time in seconds. The time must be changed keeping the environment of the server. This is because modifying the execution time will affect all the sites hosted by the server.
| Explain the purpose of output buffering in PHP. |
Output buffering in PHP buffers a script’s output. This buffer can be edited before returning it to the client. Without output buffering, PHP sends data to the web server as soon as it is ready. Output buffering “send” cookies at any point in the script. Cookies do not have to be necessarily sent near the start of the page. Output buffers are stackable and hence sending to output is by choice.
| Describe session in PHP. |
When a user logs in an application, his details are usually stored in a session variable. This information is available to all pages in one application. Sessions in PHP work using a unique id for each visitor.
Let see example :
// Start Your session
// Set session variables
$_SESSION[“Favanimal”] = “Tiger”;
$_SESSION[“Favbird”] = “Eagle”;
echo “Session variables are set.”;
| How can we know the number of days between two given dates using PHP? |
The start date and end date can be first found as shown below: $date1= strotime($start_date);
$date_diff = (($date1)- ($date2)) / (60*60*24)
| Write the statements that are used to connect PHP with MySQL |
The statements that can be used to connect PHP with MySQL is: <?
$conn = mysql_connect(‘localhost’);
This statement gets the resource of the localhost. There are other different ways with which you can connect to the database and they are as follows:
| How to use HTTP Headers inside PHP? |
Write the statement through which it can be added? HTTP headers can be used in PHP by redirection which is written as: <?header(‘Location: http://www.php.net’)?>
The headers can be added to HTTP response in PHP using the header(). The response headers are sent before any actual response being sent. The HTTP headers have to be sent before taking the output of any data. The statement above gets included at the top of the script.
| Why PHP is also called a Scripting language? |
PHP is basically a general-purpose language, which is used to write scripts. Scripts are normal computer files that consist of instructions written in PHP language. It tells the computer to execute the file and print the output on the screen. PHP is used for webpages and to create websites, thus included as a scripting language.
| Why many companies are switching their current business language to PHP? |
Where PHP basically used? PHP is rapidly gaining popularity and many companies are switching their current language for this language. PHP is a server-side scripting language. PHP executes the instructions on the server itself. The server is a computer where the web site is located. PHP is used to create dynamic pages and provides faster execution of the instructions.
| What is the use of PEAR in PHP? |
PEAR is known as PHP Extension and Application Repository. It provides a structured library to the PHP users and also gives provision for package maintenance.
| What does ODBC do in context with PHP? |
PHP supports many databases like dBase, Microsft SQL Server, Oracle, etc. But, it also supports databases like filePro, FrontBase and InterBase with ODBC connectivity. ODBC stands for Open Database connectivity, which is a standard that allows user to communicate with other databases like Access and IBM DB2.
| Why PHP is sometimes called as an embedded scripting language? |
| What is difference between require_once(), require(), include()?|
require() includes and evaluates a specific file, if the file is not found then it shows a Fatal Error.
require_once() includes only the file which is not being included before. It is used to be recommended for the files where you have lots of functions stored.
include() includes the file, even if the file is not found, but it gives a warning to the user to include().
How the web server
interprets PHP and interacts with the client?
After installing and configuring the PHP, the web When PHP is installed, the Web server looks for PHP code that is embedded in the HTML file with its extension. The extensions which are used are .php or .phtml. When a web server receives a request for the file with an appropriate extension, HTML statements are processed and PHP statements are executed on the server itself. When the processing gets over the output is being shown in HTML statements.
What is PEAR in
PEAR(PHP Extension and Application Repository) is a framework and repository for reusable PHP components. PEAR is a code repository containing all kinds of PHP code snippets and libraries.
PEAR also offers a command-line interface that can be used to automatically install “packages”.
PHP being an open
source is there any support available to it?
PHP is an open source language, and it is been said that it has very less support online and offline. But, PHP is all together a different language that is being developed by group of programmers, who writes the code. There is lots of available support for PHP, which mostly comes from developers and PHP users.
What are the steps
involved to run PHP?
The steps which are involved and required to run PHP is as follows:
1. Set up the web environment.
2. Set up the web servers. There are many web servers that are available and the mostly used is Apaches which automatically remains installed with linux distribution and on windows it is easy to install. There are other servers like IIS (Internet information server) provided by Microsoft can be used to set up the web environment.
3. Install the web server and PHP
4. Update and administer the system for changes.
What is difference
between require_once(), require(), include()?
require() includes and evaluates a specific
file, if the file is not found then it shows a Fatal Error.
require_once() includes only the file which is not being included before. It is
used to be recommended for the files where you have lots of functions stored.
include() includes the file, even if the file is not found, but it gives a
warning to the user to include().
How the web server
interprets PHP and interacts with the client?
After installing and configuring the PHP, the web When PHP
is installed, the Web server looks for PHP code that is embedded in HTML file
with its extension. The extensions which are used are .php or .phtml. When web
server receives a request for the file with an appropriate extension, HTML
statements are processed and PHP statements are executed on the server itself.
When the processing gets over the output is being shown in HTML statements.
Why IDE is
recommended for use while programming with PHP?
IDE stands for Integrated Development environment; it is a framework for developing applications. It includes programming editor where you can edit and write the development programs. The features of IDE are as follows:
1. Debugging: this is the feature which is used to debug or find the bugs in a program
2. Preview: this is the feature which allow instant preview of the program you are writing
3. Testing: this is the features that includes built in testing features through which you can check your scripts
4. FTP: through this you can upload and download the file while connecting to the server.
5. Project management: it organizes scripts into projects; manages the files in the project; includes file checkout and check-in features.
6. Backups: it creates backups automatically of your Web site at periodic intervals.
How PHP statement
is different from PHP script?
The difference between PHP statements and PHP script is that statements are a set of instructions that tell PHP to perform an action. PHP script consists of a series of PHP statements that it uses for execution. PHP executes statements one at a time till it reaches the end of the script. An example is as follows:
PHP statement: echo “Hi”;
if (time = midnight)
put on pajamas;
go to bed;
What are the
different types of statements that are present in PHP?
There are four kinds of PHP statements that are
present. They are as follows:
Simple statement– these are the echo statements and end with a semicolon
(;). PHP ignores white spaces between simple statements. Until it finds a
semicolon it reads the statement.
Complex/Conditional statements: these are the statements which deal with
certain conditions that have to be executed to meet certain specific
requirements. These are if and else block or switch statements. PHP reads the
complete statement and doesn’t stop at the first semicolon it encounters. It
looks for starting and ending braces to end the execution.
Looping statements: statements that are repeated in a block. The feature
that enables you to execute the statements repeatedly is called as loop. For
example: for loop, while loop, do..while loop.
How can we increase
the execution time of a php script?
By the use of void set_time_limit(int seconds)
Set the number of seconds a script is allowed to run. If this is reached, the script returns a fatal error. The default limit is 30 seconds or, if it exists, the max_execution_time value defined in the php.ini. If seconds is set to zero, no time limit is imposed.
When called, set_time_limit() restarts the timeout counter from zero. In other words, if the timeout is the default 30 seconds, and 25 seconds into script execution a call such as set_time_limit(20) is made, the script will run for a total of 45 seconds before timing out.
Write a Hello world
program using variable?
To write the hello world program in PHP using variable you
need to know the tags that are used in HTML and the PHP coding which is as
<head><title>Hello World Script using Variable</title></head>
$salutation = “Hello World!”;
How many different
types of messages available in PHP?
1. Error message: is received when the script has some problem that is preventing it from running correctly. The message consists of the possible solution or identification of the problem. Ex: Parse error: occurs when there is something gets missed while writing the script.
2. Warning message: is received when the script find out some problem that doesn’t allow the script to run. These messages are not of very high priority but quite essential to show that there is something wrong with the script. Ex: if you write print_r() instead of print_r($varname) then a warning will occur like this:
Warning: print_r() expects at least 1 parameter, 0 given
The script will execute in continuation.
3. Notice: is received when there is a condition where a script might have an error or may be it is working. Ex: echo variables that don’t exist.
What does type
casting mean in PHP? Explain with an example?
PHP automatically store the data and interprets according to
itself. Type casting is a way to assign the variable according to your need and
requirement and not allowing PHP to assign it automatically. To specify the
type, it can be used like:
$newint = (int) $var1;
$newfloat = (float) $var1;
$newstring = (string) $var1;
The value in the variable on the right side of the equal sign is stored in the variable on the left side as the specified type.
Explain how to
submit form without a submit button.
We can achieve the above task by using
How error handling
is being handled by PHP?
Error handling is very important in every programming
language. PHP uses the trigger to print the error in a program. The example
statement is given below:
If ($height_of_door > $height_of_house)
The E_USER_ERROR in the statement tells PHP that the condition is an error.
Impossible condition is a string message which is displayed when an error is
If the condition comes out to be true then the following message is displayed:
Fatal error: Impossible condition
E_USER_WARNING or E_USER_NOTICE can be used instead of E_USER_ERROR, to have
PHP treat the condition as a warning or notice. Own statements can be written
to perform error handling actions such as send a message, log a message or stop
If ($height_of_door > $height_of_house)
echo “This is impossible<br>”;
If $height_of_door is larger than $height_of_house, the message is echoed, and exit() stops the script.
Die statement can be used to display an error message when a function fails.
What are escaping
characters? Explain with an example?
Special characters are the characters that have some special
meaning attached to it. Example is $, #, % etc. A backslash (\) before the
special symbol is known as escaping characters. For example, two strings
produce the same output:
$string = ‘The variable name is $var1’;
Suppose you want to store a string as follows:
$string = _Where is Tom’_s house_;
The sting can be interpreted by PHP by putting a backslash (\) in front of the
single quote. The backslash tells PHP that the single quote does not have any
special meaning; it’s just an apostrophe.
$string = _Where is Tom\’_s house_;
What are the different components used in PHP for formatting?
The components that are used in PHP for
formatting are as follows:
1. %: it tells the start of the formatting instruction.
2. Padding character (pad): is used to fill out the string when the
value to be formatted is smaller than the width assigned. Pad can be a space, a
0, or any character preceded by a single quote (‘).
3. –: A symbol meaning to left-justify the characters. If this is
not included, the characters are right-justified.
4. width: The number of characters to use for the value. If the
value doesn’t fill the width, the padding character is used to pad the value.
For example, if the width is 5, the padding character is 0, and the value is 1,
the output is 00001.
5. dec: The number of decimal places to use for a number. This
value is preceded by a decimal point.
6. type: The type of value. Use s(string) for string, f (float) for
numbers that you want to format with
What is the use of
super-global arrays in PHP?
Super global arrays are built in arrays that can be used anywhere. They are also called as auto-global as they can be used inside a function as well. The arrays with the longs names such as $HTTP_SERVER_VARS must be made global before they can be used in an array. This $HTTP_SERVER_VARS check your php.ini setting for long arrays.
What is the use of
$_Server and $_Env?
$_SERVER and $_ENV arrays contain different information. The
information depends on the server and operating system being used. Most of the
information can be seen of an array for a particular server and operating
system. The syntax is as follows:
foreach($_SERVER as $key =>$value)
echo “Key=$key, Value=$value\n”;
How to create
reusable code in PHP?
Applications created in PHP often perform the same task in
same script or in different scripts. To create a reusable code functions are
used. Functions are group of PHP statements that perform a specific task.
A header and footer can be created for all the web pages which has to be used
again and again.
echo ‘<img src=”my.jpg” width=”100%” height=”7” />
<br />Cosmos Legend.
<br />Nepal </address></font>
<p>or send questions to
<a href=”mailtossdad:[email protected]”>sales </a>
<img src=”my.jpg” width=”100%” height=”7” />’;
Instead of typing header and footer for each page, a function can be created and used to add footer and header in every page. The function can be named as:
Write a program to
show the joining of two strings in PHP?
Two strings can be joined together by the use of a process
called as concatenation. A dot (.) operator is used for this purpose. Example
is as follows:
$str1 = _Hello_;
$str2 = _World!_;
$str = $str1.$str2;
What is the
difference between $argv and $argc? Give example?
To pass the information into the script from outside, help can be taken from the PHP CLI (Command-line interface) method. Suppose addition of two numbers has to be passed to PHP then it can be passed like this on the command line:
php add.php 2 3
Here the script name is add.php, and 2 and 3 are the numbers that has to be added by the script. These numbers are available inside the script in an array called
$argv. This array contains all the information on the command line; the statement is stored as follows:
So, $argv always contains at least one element — the script name.
Then, in your script, you can use the following statements:
$sum = $argv + $argv;
$argc is a variable that stores the numbers of elements in $argv. $argc is
equal to at least 1, which is saved for the name of the script.
Example is $argc=3 using the above statements.
Write a statement
to show the joining of multiple comparisons in PHP?
PHP allows multiple comparisons to be grouped together to
determine the condition of the statement. It can be done by using the following
comparison1 and|or|xor comparison2 and|or|xor comparison3 and|or|xor.
The operators that are used with comparisons are as follows:
1. and: result in positive when both comparisons are true.
2. or: result in positive when one of the comparisons or both of the
comparisons are true.
3. xor: result in positive when one of the comparisons is true but
not both of the comparisons.
$MahCity == “Mahesh” or $MahState == “Maravi”
and $name == “Abuur”