How do you upload files in PHP ?

We can upload files by using move_uploaded_file(). There are two parameters for the move_uploaded_file function. One is to specify uploaded file details and other is to specify new file details to be created.
The steps to follow are
    1) Include enctype="multipart/formdata" in the form tag.
    2) Using method post is recommended.
    3) We use $_FILES super global array to get the uploaded file details.
    4) By using $_FILES we can validate the file for size, file type.

How will you redirect to a page without header function?

By using Javascript we can redirect the page to another page. And also there are htaccess redirection techniques.

What is a common error caused with header function?

headers already sent output started at some x line is the error. This error occurs when there is an out put generated before the header function.

How do you know whether the headers are sent or not?

We have a function headers_sent(). This function is used to check whether the headers are already sent.

What is the difference between method get and method post?

The first difference is, method get is faster in performance than post. Because, by using post method the data posted is encrypted to cipher data and sent to the server. Where in get the encryption does not happens and it is faster.
    Get method can carry limited amount of data and it is less than post method.
    Post method is secure than get as the data submitted is not visible to the real world. Where as in the get method some one may see the data submitted in the URL bar.
    Using post method We can submit the data to the server only with the help of an HTML form. Where as a get method can send the data to server with a form and also with a HTML hyperlink.

What is difference between include() function and require() function?

Both the functions are used to include a PHP file in other PHP file. Generally if we have a block of source code usefull in multiple instances, then we place the block of source code in one file and will include the file in other files. The difference between include() and require() function are as follows:
    (i) If the file path mentioned with the include function is not found then it shows a warning message and continues the execution of the script. Where as require function results a fatal error and stops the execution of the script.
    (ii) The second difference is include function is faster in execution than require function. Because with the require function the parser will check whether the file exists or not. Where as the include function does not bothere about the file is there or not.

How many types of comments are there in PHP?

There are two types of comments in PHP. They are

1. One Line comments (// or #)
2. Multiple Line comments (/* */)

The "one-line" comment styles only comment to the end of the line or the current block of PHP code, whichever comes first.
Eg:

      

     <?

      // echo 'Your code upto end of the line'; 

     ?>

     <?

     # echo 'Your code upto end of the line';  

     ?> 

Multiple Line comments (/* */) are used to comment a large block of PHP code.
Ex: <?

 /*
    echo 'This is a test';

    echo 'This is a test line2';

       echo 'This is a test line 3';
 */
?>