PHP

1
PHP

• By
• Sergio Rodriguez

2
PHP

• PHP Hypertext Preprocessor
• Scripting language

3
History

• 1994 - Written by Rasmus Lerdorf
• 1997 - Zeev Suraski and Andi Gutmans
• Rewrote parser
• PHP 2

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History

• 1998 - PHP 3
• 2000 - PHP 4
• Still being developed
• Version 4.4.7 - Oct. 2007
• 2004 - PHP 5

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Usage

• Server-side Scripting
• Web development
• Command-line Scripting
• Shell scripting
• Client-side GUI Apps
• Not very common

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Server-side Scripting

• Main use
• Code embedded in HTML to create dynamic web pages
• LAMP Architecture
• Advantage over others
• but first!

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Syntax

• Advantage Similar to high level PLs we are
  familiar with
• PHP code goes between tags
• lt?php --CODE-- ?gt
• Features that make it different

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Syntax

• Embedding HTML in PHP control structures
• Will output anything between ?gt and the next
  lt?php tags

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Types

• Type is not explicitly set for variable by
  programmer
• Type of variable is juggled throughout PHP code
• Criticism due to this (errors not detected at
  compile time)

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Types

• Eight different types
• Boolean
• Integer
• Float AKA Double
• String
• Array
• Object
• Resource
• Null

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Boolean

• Trivial
• Cast as (bool) or (boolean)
• False is
• Integer - 0
• Float - 0.0
• String - Empty or 0
• NULL
• Array - Size 0 among others
• True is everything else

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Integer

• No unsigned integers in PHP
• Include octal and hexadecimal numbers
• Octal - 00-7
• Hex - 0xX0-9a-fA-F
• Overflow? Treats value as float
• No division operator - yields float
• Cast as (int) or (integer)
• From float to integer - rounding towards zero

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Float (Double)

• Loss of precision when converted to internal
  binary
• Ex floor((0.10.7)10) is 7, not 8
• Cast as (float), (double), or (real)

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String

• No bound to size of strings
• Single quotes
• Escape or \ characters
• Double quotes
• More escaped characters (\n, \t, \\, etc)

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Array

• (key, value) pairs
• Key may be an integer index, like Java arrays
• print_r(arr) //Prints out array

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Object

• Use new to create new instance
• Cast as (object) - new instance of built-in class
  stdClass
• scalar member contains value

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Resource

• A resource is a special variable, holding a
  reference to an external resource. Taken from
  the PHP Documentation
• i.e. Connectors to DBs (mySQL, MSSQL, etc)

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Variables

• Start with , followed by underscore or letter,
  and then followed by (number letter
  underscore)
• Dynamic Scoping
• Variable variables
• Hold variable name as string

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Operators

• Same as other PLs
• , !
• echo shell command
• . (Yeah, thats it)
• Arrays
• , and equality across key/value pairs
• Instanceof (Looks familiar?)

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Functions

• Again, similar to what we already know
• C-style
• i.e. function foo(myVal 44)/BODY/
• return arrays to list
• Store function name in variable

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Objects

• Nothing new
• parent - used in inheritance, refers to base
  class
• PHP 5 is more extensive

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References

• Wikipedia - PHP
• http//en.wikipedia.org/wiki/PHP
• PHP Manual
• http//www.php.net/manual/en/index.php