PHP interview questions

What is PHP?

PHP (Hyper text Pre Processor) is a scripting language commonly used for web applications. PHP can be easily embedded in HTML. PHP generally runs on a web server. It is available for free and can be used across a variety of servers, operating systems and platforms.

What Is a Session in PHP?

A PHP session is no different from a normal session. It can be used to store information on the server for future use. However this storage is temporary and is flushed out when the site is closed. Sessions can start by first creating a session id (unique) for each user.

Syntax : session_start()

E.g. storing a customer’s information.

Explain the difference between $message and $$message.

$message is used to store variable data. $$message can be used to store variable of a variable. Data stored in $message is fixed while data stored in $$message can be changed dynamically.

E.g. $var1 = ‘Variable 1’

$$var1= ‘variable2’

This can be interpreted as $ Variable 1=‘variable2’;

For me to print value of both variables, I will write

$var1 $($var1)

What Is a Persistent Cookie?

Cookies are used to remember the users. Content of a Persistent cookie remains unchanged even when the browser is closed. ‘Remember me’ generally used for login is the best example for Persistent Cookie.

Explain the differences between require and include, include_once.

Include () will include the file specified.

Include_once () will include the file only once even if the code of the file has been included before.

Require () and include () are the same with respect to handling failures. However, require () results in a fatal error and does not allow the processing of the page.

What is urlencode and urldecode?

Urlencode can be used to encode a string that can be used in a url. It encodes the same way posted data from web page is encoded. It returns the encoded string.

Syntax: urlencode (string $str )

Urldecode can be used to decode a string. Decodes any %## encoding in the given string (Inserted by urlencode)

Syntax: urldecode (string $str )

What are the different types of errors in PHP?

Different types of errors are:

E_ERROR: A fatal error that causes script termination

E_WARNING: Run-time warning that does not cause script termination

E_PARSE: Compile time parse error.

E_NOTICE: Run time notice caused due to error in code

E_CORE_ERROR: Fatal errors that occur during PHP's initial startup (installation)

E_CORE_WARNING: Warnings that occur during PHP's initial startup 

E_COMPILE_ERROR: Fatal compile-time errors indication problem with script.

E_USER_ERROR: User-generated error message. 

E_USER_WARNING: User-generated warning message. 

E_USER_NOTICE: User-generated notice message. 

E_STRICT: Run-time notices.

E_RECOVERABLE_ERROR: Catchable fatal error indicating a dangerous error

E_ALL: Catches all errors and warnings 

Explain how to
submit form without a submit button.



A form data can be posted or submitted without the
button in the following ways:



1. On OnClick event of a label in the form, a
JavaScript function can be called to submit the form



e.g. document.form_name.submit()



2. Using a Hyperlink: On clicking the link, JavaScript
function can be called



e.g <a.href=” javascript:document.MyForm.submit();">





What
are the functions for IMAP? 



IMAP
is used for communicate with mail servers. It has a number of functions. Few of
them are listed below:



Imap_alerts
– Returns all the imap errors occurred



Imap_body
– Reads the message body



Imap_check
– Reads the current mail box



Imap_clearflag_full
– Clears all flags



Imap_close
– close and IMAP stream



Imap_delete
– Delete message from current mailbox



Imap_delete_mailbox
– Deletes a mailbox



Imap_fetchbody
– Fetches body of message



Imap_fetchheader
– Fetches header of message



Imap_headers
– Returns headers for ALL messages



Imap_mail
: send a mail



Imap_sort-
Sorts imap messages





How
can we increase the execution time of a php script? 



Default time allowed for the PHP scripts to execute is
30s defined in the php.ini file. The function used is set_time_limit(int
seconds). If the value passed is ‘0’, it takes unlimited time. It should be
noted that if the default timer is set to 30 sec and 20 sec is specified in
set_time_limit(), the script will run for 45 secs.



How to set
cookies in PHP? 



Cookies
are often used to track user information. 



Cookies
can be set in PHP using the setcookie() function.



Parameters are : name of the cookie, Value of cookie,
time for expiry of cookie, path of the cookies location on server, domain,
secure (TRUE or FALSE) indication whether the cookie is passed over a secure
HTTPS, http only (TRUE) which will make the cookie accessible only through
HTTP.



Returns TRUE or FALSE depending on whether the cookie
was executed or not.




What is Type juggle in php?



Type Juggling means
dealing with a variable type. In PHP a variables type is determined by the
context in which it is used. If an integer value is assigned to a variable, it
becomes an integer.



E.g. $var3= $var1 + $var2



Here, if $var1 is an integer. $var2 and $var3 will also
be treated as integers.  





Explain the difference between include
and require. 



Require () and include () are the same with respect to
handling failures. However, require () results in a fatal error and does not allow
the processing of the page. i.e. include will allow the script to continue. 

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