Php Interview Questions and Answers -02

How do you define a constant?
Via define() directive, like define (“MYCONSTANT”, 100);

What are the differences between require and include, include_once? 
Anwser 1:
require_once() and include_once() are both the functions to include and evaluate the specified file only once. If the specified file is included previous to the present call occurrence, it will not be done again.

But require() and include() will do it as many times they are asked to do.

Anwser 2:
The include_once() statement includes and evaluates the specified file during the execution of the script. This is a behavior similar to the include() statement, with the only difference being that if the code from a file has already been included, it will not be included again. The major difference between include() and require() is that in failure include() produces a warning message whereas require() produces a fatal errors.

Anwser 3:
All three are used to an include file into the current page.
If the file is not present, require(), calls a fatal error, while in include() does not.
The include_once() statement includes and evaluates the specified file during the execution of the script. This is a behavior similar to the include() statement, with the only difference being that if the code from a file has already been included, it will not be included again. It des not call a fatal error if file not exists. require_once() does the same as include_once(), but it calls a fatal error if file not exists.

Anwser 4:
File will not be included more than once. If we want to include a file once only and further calling of the file will be ignored then we have to use the PHP function include_once(). This will prevent problems with function redefinitions, variable value reassignments, etc.

What is meant by urlencode and urldecode?
Anwser 1:
urlencode() returns the URL encoded version of the given string. URL coding converts special characters into % signs followed by two hex digits. For example: urlencode(“10.00%”) will return “10%2E00%25”. URL encoded strings are safe to be used as part of URLs.
urldecode() returns the URL decoded version of the given string.

Anwser 2:
string urlencode(str) – Returns the URL encoded version of the input string. String values to be used in URL query string need to be URL encoded. In the URL encoded version:

Alphanumeric characters are maintained as is.
Space characters are converted to “+” characters.
Other non-alphanumeric characters are converted “%” followed by two hex digits representing the converted character.

string urldecode(str) – Returns the original string of the input URL encoded string.

For example:

$discount =”10.00%”;
$url = “http://domain.com/submit.php?disc=”.urlencode($discount);
echo $url;

You will get “http://domain.com/submit.php?disc=10%2E00%25”.

How To Get the Uploaded File Information in the Receiving Script? 

Once the Web server received the uploaded file, it will call the PHP script specified in the form action attribute to process them. This receiving PHP script can get the uploaded file information through the predefined array called $_FILES. Uploaded file information is organized in $_FILES as a two-dimensional array as:
$_FILES[$fieldName][‘name’] – The Original file name on the browser system.
$_FILES[$fieldName][‘type’] – The file type determined by the browser.
$_FILES[$fieldName][‘size’] – The Number of bytes of the file content.
$_FILES[$fieldName][‘tmp_name’] – The temporary filename of the file in which the uploaded file was stored on the server.
$_FILES[$fieldName][‘error’] – The error code associated with this file upload.

The $fieldName is the name used in the <INPUT TYPE=FILE, NAME=fieldName>.

What is the difference between mysql_fetch_object and mysql_fetch_array? 
MySQL fetch object will collect first single matching record where mysql_fetch_array will collect all matching records from the table in an array

How can I execute a PHP script using command line? 
Just run the PHP CLI (Command Line Interface) program and provide the PHP script file name as the command line argument. For example, “php myScript.php”, assuming “php” is the command to invoke the CLI program.
Be aware that if your PHP script was written for the Web CGI interface, it may not execute properly in command line environment.

I am trying to assign a variable the value of 0123, but it keeps coming up with a different number, what’s the problem? 
PHP Interpreter treats numbers beginning with 0 as octal. Look at the similar PHP interview questions for more numeric problems.