CURL means Client URL Library curl is a command line tool for transferring files with URL syntax, supporting FTP, FTPS, HTTP, HTTPS, SCP, SFTP, TFTP, TELNET, DICT, LDAP, LDAPS and FILE. 

curl supports SSL certificates, HTTP POST, HTTP PUT, FTP uploading, HTTP form based upload, proxies, cookies, user+password authentication (Basic, Digest, NTLM, Negotiate), file transfer resume, proxy tunneling and a busload of other useful tricks. 

CURL allows you to connect and communicate to many different types of servers with many different types of proto
cols. libcurl currently supports the http, https, ftp, gopher, telnet, dict, file, and ldap protocols. libcurl also supports HTTPS certificates, HTTP POST, HTTP PUT, FTP uploading (this can also be done with PHPs ftp extension), HTTP form based upload, proxies, cookies, and user+password authentication

Ans: There are some differenc between GET and POST method. They are:
  ♦ GET method is used for submitting small amount of data. But POST method is used for submitting large amount of data.
  ♦   When we use GET method requested data show in url but not in POST method so , POST method  is good for sending sensitive request.

If the try to copy a referenced object. It will simply point back to the addrassing location of the original object To remedy the problems with copying, PHP offers an explicit means for cloning an object is known as object cloning.

Type casting: Converting values from one data type to another is known as type casting.
Type Juggling: Variables are sometimes automatically cast to best fit the circumstances in which they are referenced.

The advantages of object-oriented programming are:
The complexity of the software can be merged easily.
The data hiding concept helps the programmer to build secure programs.
Through class concept we can define the defined types
New data and functions can be easily coded whenever necessary.pt we can define the user defined data types.