The header() function sends a raw HTTP header to a client. We can use header() function for redirection of pages. It is important to notice that  header()  must be called before any actual output is seen..

array_flip exchange the keys with their associated values in array ie. Keys becomes values and values becomes keys.

<?php
$arrayName    = array("course1"=>"php","course2"=>"html");
$new_array    = array_flip($arrayName);
print_r($new_array);
?>

OUTPUT :

Array
(
[php]     => course1
[html]    => course2
)

The dba_insert() function adds a record to a database.

<?php
$tomorrow = mktime(0, 0, 0, date("m") , date("d")+1, date("Y"));
$lastmonth = mktime(0, 0, 0, date("m")-1, date("d"), date("Y"));
echo ($tomorrow-$lastmonth)/86400;
?>

We can use the preg_match() function with “/.*@(.*)$/” as the regular expression pattern.
For example:
preg_match("/.*@(.*)$/","https://info@abc.com",$data);
echo $data[1];
?>

PHP developed for less script, time saving, Free Open Source Software and runs on different platforms such as Windows, Linux, Unix, etc. PHP compatible with almost all servers used today such as Apache, IIS, etc.

The PHP scripting language resembles JavaScript, Java, and Perl, These languages all share a common ancestor, the C programming language. PHP has full access to the information that the server has, and very little access to information that the client has. In fact, it only has information that the client tells the server and that the server passes on to PHP. Because it is on the server, however, PHP cannot be modified by the client. While you cannot necessarily trust the information that the client gives to PHP, you can trust that your PHP is doing what you told it to do. Because PHP is on the server end, your PHP scripts can affect your server -- such as by keeping an activity log or updating a database.

JavaScripts uses a hierarchical structure that applies to the objects in a document. There are some objects that show the relationship of one object to another using the language.

Window object: This is the topmost object in the hierarchy. It represent the content area of browser window that consists of HTML documents. Each frame is also a window that has some actions inside it.

Document object: This object gets loaded in a window and consists of objects of different kind in the model. It consists of the content that will be written in the script.

Form object: Form objects are used for more interaction with the users. It represents the form elements inside <FORM>...</FORM> tag.