introduction to PHP

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Introduction ToPHP
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• PHP originally stood for "Personal Home Page".
• The PHP Hypertext Preprocessor (PHP) is a
  programming language that allows web developers
  to create dynamic content that interacts with
  databases.
• PHP supports many databases (MySQL, Informix,
  Oracle, Sybase, Solid, PostgreSQL, Generic ODBC,
  etc.)
• PHP is a server-side scripting language, like ASP
  
• PHP is an open source language.PHP is basically
  used for developing web based software
  applications

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Common uses of PHP

• PHP performs system functions, i.e. from files on
  a system it can create, open, read, write, and
  close them.
• PHP can handle forms, i.e. gather data from
  files, save data to a file, through email you can
  send data, return data to the user.
• You add, delete, modify elements within your
  database through PHP.
• Access cookies variables and set cookies.
• Using PHP, you can restrict users to access some
  pages of your website.
• It can encrypt data.

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Characteristics of PHP

• Five important characteristics make PHP's
  practical nature possible -
• Simplicity
• Efficiency
• Security
• Flexibility
• Familiarity

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Features

• In PHP there is no need to specify data type for
  variable declaration. Rather, it can be
  determined at the time of execution depends on
  the value of the variable. So that, PHP is called
  as loosely typed language.
• PHP provides cross platform compatibility, unlike
  some other server side scripting language.
• PHP programming structure includes variable
  variables that is, the name of the variable can
  be change dynamically.
• This language contains access monitoring
  capability to create logs as the summary of
  recent accesses

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• Predefined error reporting constants are
  available to generate a warning or error notice.
  For example, when E_STRICT is enabled, a warning
  about deprecated methods will be generated.
• PHP supports extended regular expression that
  leads extensive pattern matching with remarkable
  speed.
• Since PHP is a single inheritance language, the
  parent class methods can be derived by only one
  directly inherited sub class. But, the
  implementation of traits concept, reduce the gap
  over this limitation and allow to reuse required
  method in several classes.

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"Hello" Script in PHP

• To get a feel for PHP, first start with simple
  PHP scripts. Since "Hello, World!" is an
  essential example, first we will create a
  friendly little "Hello, World!" script.
• As mentioned earlier, PHP is embedded in HTML.
  That means that in amongst your normal HTML (or
  XHTML if you're cutting-edge) you'll have PHP
  statements like this
• lthtmlgt
• ltheadgt
• lttitlegt Hello Worldlt/titlegt
• lt/headgt
• ltbodygt
• lt?php echo Hello! ?gt
• lt/bodygt
• lt/htmlgt
• It will produce following result -
• Hello!

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• If you examine the HTML output of the above
  example, you'll notice that the PHP code is not
  present in the file sent from the server to your
  Web browser. All of the PHP present in the Web
  page is processed and stripped from the page the
  only thing returned to the client from the Web
  server is pure HTML output.
• Most Basic PHP Syntax A PHP scripting block
  always starts withlt?php and ends with ?gt . A PHP
  scripting block can be placed anywhere in the
  document

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• PHP Variable DeclarationAll variables in PHP
  begin with the sign.Ex.lt?phpmy_variable
  20my_variable2 Hello World?gt
• Variable RulesYou have to follow some rules when
  naming a variableA variable name cannot contain
  spaces.
• A variable name must start with a letter or an
  underscore ( _ )
• A variable name can only contain alpha-numeric
  characters and underscores (a-z, A-Z, 0-9, and _
  )
• String Variableslt?phpmy_string Hello
  everybodyecho my_string?gt

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• strlen() functionThe PHP strlen() used to get
  length of stringlt?phpecho strlen("Im sorry
  dave, Im afraid I cant do that.")?gtThe
  result of the statement will be a number (the
  length of the string including space and signs,
  not only the characters), in this case the number
  43.
• strpos() functionThe PHP strpos() function is
  used to search for a character or string within a
  string. If the character is found the strpos()
  function will return the position of the first
  match. If strpos() cant find the character in
  the string, it will return FALSE.lt?phpecho
  strpos(Open the pod bay doors please,
  HAL,HAL)echo strpos(Open the pod bay doors
  please, HAL,H)?gtThe position of the string
  HAL in the whole string is position 31 (the
  space before the string HAL.) The reason that it
  is 31 (space) and not 32 (the character H) is
  that the first position in the string is 0, and
  not 1.

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• Concatenation OperatorPHP has only one string
  operator. If you want to put two string values
  together you can use the concatenation operator
  (.) lt?phpstr_oneHellostr_twoWorld!e
  cho str_one . . str_two?gtThe result will
  be Hello World!.