Php interview questions

1)What’s the difference between include and require? - It’s how they handle failures. If the file is not found by require(), it will cause a fatal error and halt the execution of the script. If the file is not found by include(), a warning will be issued, but execution will continue.

2)Explain the ternary conditional operator in PHP? - Expression preceding the ? is evaluated, if it’s true, then the expression preceding the : is executed, otherwise, the expression following : is executed.

3)For printing out strings, there are echo, print and printf. Explain the differences. - echo is the most primitive of them, and just outputs the contents following the construct to the screen. print is also a construct (so parentheses are optional when calling it), but it returns TRUE on successful output and FALSE if it was unable to print out the string. However, you can pass multiple parameters to echo, like:



and it will output the string "Welcome to TechInterviews!" print does not take multiple parameters. It is also generally argued that echo is faster, but usually the speed advantage is negligible, and might not be there for future versions of PHP. printf is a function, not a construct, and allows such advantages as formatted output, but it’s the slowest way to print out data out of echo, print and printf.

4)What’s the difference between htmlentities() and htmlspecialchars()? - htmlspecialchars only takes care of <, >, single quote ‘, double quote " and ampersand. htmlentities translates all occurrences of character sequences that have different meaning in HTML.

5)What is the use of ob_start() in PHP?
Actually, ob_start() tells PHP to start output buffering, meaning that anything you output after ob_start() wont be sent to the browser until the end of the page or ob_end() etc are reached.

So that means that once you use ob_start() and echo something out, you can still set cookies without any errors. For example:


ob_start();
echo "this will work";
setcookie("test", true);

ob_end_flush();

?>

6)what is the difference between ph4 and php5
In PHP4, everything was passed by value, including objects. This has changed in PHP5 -- all objects are now passed by reference.
PHP5 introduces a new unified constructor/destructor names. In PHP4, a constructor was simply a method that had the same name as the class itself. This caused some headaches since if you changed the name of the class, you would have to go through and change every occurrence of that name.

In PHP5, all constructors are named __construct(). That is, the word construct prefixed by two underscores. Other then this name change, a constructor works the same way.Also, the newly added __destruct() (destruct prefixed by two underscores) allows you to write code that will be executed when the object is destroyed.

Type Hinting

PHP5 introduces limited type hinting. This means you can enforce what kind of variables are passed to functions or class methods. The drawback is that (at this time), it will only work for classes or arrays -- so no other scalar types like integers or strings.
PHP finally introduces exceptions! An exception is basically an error. By using an exception however, you gain more control the simple trigger_error notices we were stuck with before.
Standard PHP Library
use this link to know more
http://prakashadmane.blogspot.com/2008_01_01_archive.html

7)What are the differences between Get and post methods

1. By using Post method we can send unlimited data,But it's
not possible in the case of Get. Get support maximum 200
characters or 2 MB data.
2. Get method is not secure as anyone can see it's content
in the URL.It doesn't happen in case of Post method.

8)How can we submit a form without a submit button?

using javascript
document.form.submit();
9)How many ways we can retrieve the date in result set of mysql using php?

4 ways

1. mysql_fetch_rows
2. mysql_fetch_object
3. mysql_fetch_assoc
4. mysql_fetch_array

mysql_fetch_object : will return the results from database
as objects. fields will be accessible like in objects
i.e $result->name,$result->cust_name

mysql_fetch_array : will return the results from database as
array. fields will be accessible like in objects
i.e $result[name],$result[cust_name]

10)What is the difference between $message and $$message?


$Message = "php";
$you= "java";

echo $message //Output:- php
echo $$message //output :-java

It means
$message is a variable and
$$Message is variable of variable

A variable of variable allows us to change the name of
variable dinamically