sort() , rsort(), asort()
ksort()   , usort()
arsort()  , uksort()
natsort() , natcasesort()
array_multisort()

unlink()-deletes the given file from the file system.
unset() -makes a variable undefined.

1 : InnoDB provides us row level locking while MyISAM provides us table level locking.

2 : InnoDB offers foreign key constraints wheres in MyISAM does not have foreign key constraints.

3 : InnoDB does not have full text search wheres MyISAM provides us full text search.

mysql_fetch_array:
Fetch a result row as an associative array and a numeric array.

mysql_fetch_object:
Returns an object with properties that correspond to the fetched row and moves the internal data pointer ahead. Returns an object with properties that correspond to the fetched row, or FALSE if there are no more rows.

mysql_fetch_row():
Fetches one row of data from the result associated with the specified result identifier. The row is returned as an array. Each result column is stored in an array offset, starting at offset 0.

Notices: These are trivial, non-critical errors that PHP encounters while executing a script - for example, accessing a variable that has not yet been defined. By default, such errors are not displayed to the user at all - although, as you will see, you can change this default behaviour.

Warnings: These are more serious errors - for example, attempting to include() a file which does not exist. By default, these errors are displayed to the user, but they do not result in script termination.

Fatal errors: These are critical errors - for example, instantiating an object of a non-existent class, or calling a non-existent function. These errors cause the immediate termination of the script, and PHP’s default behaviour is to display them to the user when they take place.

On the server side, the main difference between GET and POST is where the submitted is stored. The $_GET array stores data submitted by the GET method. The $_POST array stores data submitted by the POST method.

On the browser side, the difference is that data submitted by the GET method will be displayed in the browser’s address field. Data submitted by the POST method will not be displayed anywhere on the browser.

GET method is mostly used for submitting a small amount and less sensitive data.
POST method is mostly used for submitting a large amount or sensitive data.

"==" checks equality only,
"===" checks for equality as well as the type.

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.