PHP:  Hypertext Preprocessor is a widely used, general-purpose scripting language that was originally designed  to produce dynamic web pages for web development

A server side scripting language widely used for web applications

PHP is an interpreted language

 Both syntax are used for including the files in the php files , but the difference is ,  If the file is not found by require(), it will cause a fatal error and stop the execution of the script. If the file is not found by include(), a warning will be issued, but execution will not stop .

 

 Session is used for state management; Sessions allow data or information to be shared in all page of the website. Session variable is used to hold values of the current session, Session data is temporary and information is available until the user left the website URL. Each session is identified by a unique Id number for every visitor, The first step to use PHP session in the PHP page is to start the session with session_start(); example: session_start(); $_SESSION[‘test’]=1;

 

 $message is used to store variable data. $$message can be used to store variable of a variable.

 

Constants in PHP are defined using define() directive, like define("MYCONSTANT", 100);

 Yes, internally PHP will cast everything to the integer type, so numbers 10 and 11 will be compared.

 Expression preceding the ? is evaluated, if it’s true, then the expression preceding the : is executed, otherwise, the expression following : is executed.

 

  func_num_args() function returns the number of parameters/arguments passed to a function in PHP.

 

In PHP, :: is allowed to access methods that can perform static operations, i.e. those, which do not require object initialization.

 

 Everything is passed by value. In PHP-4 version  it's true, BUT in PHP-5 version its not - all objects are passed by reference.

 

 parent::constructor($value)

               __sleep returns the array of all the variables than need to be saved, while __wakeup retrieves them.

 

 Since the data inside the single-quoted string is not parsed for variable substitution, it’s always a better idea speed-wise to initialize a string with single quotes, unless you specifically need variable substitution.

htmlspecialchars only takes care of <, >, single quote ‘, double quote " and ampersand. htmlentities translates all occurrences of character sequences that have different meaning in HTML.

 

The main difference is the length of the hash code generated. CRC32 is, evidently, 32 bits, while sha1() returns a 128 bit value, and md5() returns a 160 bit value.

 Expression preceding the ? is evaluated, if it’s true, then the expression preceding the : is executed, otherwise, the expression following : is executed.

 

func_num_args() function returns the number of parameters/arguments passed to a function in PHP.

 

 

The major difference is the length of the hash generated. CRC32 is, evidently, 32 bits, while sha1() returns a 128 bit value, and md5() returns a 160 bit value. This is important when avoiding collisions.

 

 Crypto usage in PHP is simple, but that doesn’t mean it’s free. First off, depending on the data that you’re encrypting, you might have reasons to store a 32-bit value in the database instead of the 160-bit value to save on space. Second, the more secure the crypto is, the longer is the computation time to deliver the hash value. A high volume site might be significantly slowed down, if frequent md5() generation is required.

 

 

The main idea behind this is to use Java script submit() function in order to submit the form without clicking any submit button

 

1. mysql_fetch_row. 2. mysql_fetch_array 3. mysql_fetch_object 4. mysql_fetch_assoc

We can create MySQL database with the use of mysql_create_db(“Database Name”)

 

unlink() is a function for file system handling. It will simply delete the file in context. unset() is a function for variable management. It will make a variable undefined

 

 a) sizeof($array) – This function is an alias of count() 

b) count($urarray) – This function returns the number of elements in an array.

 

 Database name: 64 characters Table name: 64 characters Column name: 64 characters

 

 HP4 cannot support oops concepts and Zend engine 1 is used. PHP5 supports oops concepts and Zend engine 2 is used. Error supporting is increased in PHP5. XML and SQLLite will is increased in PHP5

 

 nl2br() inserts a HTML tag 

before all new line characters in a string. echo nl2br(“god bless you”); output: god bless

 

 session_id() returns the session id for the current session.

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

 

htaccess files are configuration files of Apache Server which provide a way to make configuration changes on a per-directory basis. A file, containing one or more configuration directives, is placed in a particular document directory, and the directives apply to that directory, and all subdirectories thereof.

 

How can we get second of the current time using date function?

 $second = date("s");

 

 By using $_SERVER['HTTP_USER_AGENT']

session_set_save_handler() sets the user-level session storage functions which are used for storing and retrieving data associated with a session. This is most useful when a storage method other than those supplied by PHP sessions is preferred. i.e. Storing the session data in a local database.

 

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, kerberos…), 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 protocols. 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, HTTP form based upload, proxies, cookies, and user+password authentication.

 

 Joomla is a content management system. Powerful online applications and web sites are build using Joomla. Joomla is an open source CMS tool. Clients can easily manage their web sites with minimal amount of instructions. It is highly extensible. Joomla runs off PHP or MySQL. Joomla is used to create, maintain a structured, flexible portal, add or edit content, changes the look and feel of the site. PHP scripting is used and persisted most of its data / information in MySQL database

 

 Zend Engine is used internally by PHP as a complier and runtime engine. PHP Scripts are loaded into memory and compiled into Zend opcodes

 

 Echo can accept multiple expressions while print cannot. With respect to performance echo is faster than print since it does not return a value. Print returns 1 or 0 depending on the success.

 

 CAPTCHA is a test to determine if the user using the system (usually a web form) is a human. It identifies this by throwing challenges to users. Depending on the responses the identification can be made. E,g Answering to identification of distorted images. Captcha Creator is a PHP Script that generates Strong Captchas

 

 Notify URL and Return URL is used in Paypal Payment Gateway integration. Notify URL is used by PayPal to post information about the transaction. Return URL is sued by the browser; A url where the user needs to be redirected on completion of the payment process.

 

PEAR is known as PHP Extension and Application Repository. It provides structured library to the PHP users and also gives provision for package maintenance.

 

 require() includes and evaluates a specific file, if the file is not found then it shows a Fatal Error. require_once() includes only the file which is not being included before. It is used to be recommended for the files where you have lots of functions stored. include() includes the file, even if the file is not found, but it gives a warning to the user to include().

 

Super global arrays are the built in arrays that can be used anywhere. They are also called as auto-global as they can be used inside a function as well. The arrays with the longs names such as $HTTP_SERVER_VARS, must be made global before they can be used in an array. This $HTTP_SERVER_VARS check your php.ini setting for long arrays.

 

$_SERVER and $_ENV arrays contain different information. The information depends on the server and operating system being used. Most of the information can be seen of an array for a particular server and operating system. The syntax is as follows: foreach($_SERVER as $key =>$value) { echo “Key=$key, Value=$value ”; }

 

 MySQL fetch object will collect first single matching record where mysql_fetch_array will collect all matching records from the table in an array

 

 eregi_replace() function is identical to ereg_replace() except that it ignores case distinction when matching alphabetic characters.

session_unregister() - Unregister a global variable from the current session session_unset() - Free all session variables

 

The major difference is the length of the hash generated. CRC32 is, evidently, 32 bits, while sha1() returns a 128 bit value, and md5() returns a 160 bit value. This is important when avoiding collisions.

MIME is Multipurpose Internet Mail Extensions is an Internet standard for the format of e-mail. However browsers also uses MIME standard to transmit files. MIME has a header which is added to a beginning of the data. When browser sees such header it shows the data as it would be a file

 

mysql_fetch_array() -> Fetch a result row as a combination of associative array and regular array. mysql_fetch_object() -> Fetch a result row as an object. mysql_fetch_row() -> Fetch a result set as a regular array().

 

nl2br() inserts a HTML tag 

before all new line characters in a string.