"$_GET[ ], $_POST[ ], $_REQUEST[ ], $_SERVER[ ], $_SESSION[ ], $GLOBAL[ ], $_COOKE[ ], $_FILES[ ], $_ENV[ ], "

strstr():
       The strstr() function returns the remainder of a string beginning with the first occurrence of a predefined string.Its prototype follows:            
                   string strstr(string str, string occurrence[,bool before_needle]) 
stristr(): 
       Same as strstr() function except the search of for the pattern in case insensitive.

Regular expression provide the foundation of describing or matching data according to defined syntax rules. A regular expression is nothing more than a pattern of characters itself, matched against a certain parcel of text.

Constructor: A constructor is defined as a block of code that automatically executes at the time of object instantiation. Constructors can accept parameters, call class methods or  other functions.PHP recognizes constructor by the  name__construct.  The general  Syntax→
        function__construct([argument1,argument2,….,argumentN]){ 
            //Class initialization code  
        } 
Destructor:  We can use destructors to modify the object destruction process.Derstructors are  created like any other method but must be titled    __destruct().   Syntax→     
function__destruct().

To remedy the problems with copying ,PHP offers an explicit means for cloning an object.We clone an object by prefacing it with the clone keyword, like so:
              destinationObject = clone targetObject;