PHP Data Types

1
PHP Data Types

• PHP supports 8 data types
• boolean, integer, float, string (scalar types)
• array, object (compound types)
• resource, NULL (special types)

2
PHP booleans

• Use keywords true or false
• Both are case insensitive
• Can typecast a value to boolean, using (bool) or
  (boolean)
• Usually not necessary automatic conversion to
  boolean if boolean value is needed

3
PHP booleans

• When converted to boolean, the following values
  are considered false
• boolean false, integer 0, float 0.0, empty
  string, string 0, an array with 0 elements, an
  object with 0 member variables, the special type
  NULL
• everything else is true

4
PHP integers

• Positive or negative
• Decimal, hex, or octal notation
• num1 879 // decimal notation
• num2 0xAB45 // hex notation
• num3 047 // octal notation

5
PHP floating point numbers

• Positive or negative
• a 1.234
• b 1.2e3
• c 7E-10
• / If an integer value overflows, it is
  automatically converted to a float /

6
PHP strings

• A string is a series of characters (there is no
  size limitation)
• Single quotes
• Double quotes
• heredoc syntax

7
PHP strings single quotes

• No expansion of variables and escape sequences,
  except and \
• // Outputs Arnold once said "I'll be back"echo
  'Arnold once said "I\'ll be back"'
• // Outputs You deleted C\.?echo 'You deleted
  C\\.?'
• // Outputs You deleted C\.?echo 'You deleted
  C\.?'

8
PHP strings double quotes

• Expansion of variables and escape sequences
• \ ?
• \\ ? \
• \ ?
• \t, \n, ? tab, new line, ..
• num ? value of num

9
PHP strings Heredoc syntax

• ltltlt followed by an identifier
• Same identifier to close the quotation, followed
  by a semicolon ( )
• Closing identifier must begin in the first column
  of the line
• No space or tab before or after the semicolon

10
PHP strings Heredoc syntax

• Variables are evaluated
• Escape sequences are evaluated

11
PHP strings Heredoc

• name PHP
• version 4.2
• echo ltltltEOTMy name is "name\n\n\n\n
  My version is versionEOT

12
PHP strings Heredoc

• str ltltltEODExample of stringltBRgtspanning
  multiple linesltBRgtusing heredoc syntax.EOD

13
PHP strings Useful functions

• str This is a test
• first str0 T
• strlen returns the length of a string
• length strlen( str )
• echo length 14
• more str.HI
• echo more This is a testHI

14
PHP back quotes

• Can use back quotes to execute UNIX command (same
  as Perl)
• today date
• today contains output of UNIX command data
• Can also do
• echo date

15
PHP arrays

• An array in PHP is actually an ordered map
• A map is a type that maps values to keys.
  (associative array in Perl)
• This type is optimized in several ways
• ? you can use it as a real array, or a list
  (vector), hashtable (which is an implementation
  of a map), dictionary, collection, stack, queue
  and probably more.

16
PHP arrays

• Syntax
• array( key gt value , ... )
• // key may be an integer or string
• / if it is a float, it will be truncated to an
  integer /
• // value may be any value

17
PHP arrays

• arr array(ct366" gt Perl", 60 gt Pass)
• echo arrct366" // Perl
• echo arr60    // Pass

18
PHP arrays

• If you do not specify a key for a given value,
  then the maximum of the integer indices is taken,
  and the new key will be that maximum value 1.
• // This array is the same as ...array(5 gt 43,
  32, 56, "b" gt 12)
• // ...this arrayarray(5 gt 43, 6 gt 32, 7 gt 56,
  "b" gt 12)
• If you specify a key that already has a value
  assigned to it, that value will be overwritten.

19
PHP arrays Modifying, deleting values

• arr array( 56, 67, 89 )
• arr1 100 67 changed into 100
• arr 300 default is index 3
• unset( arr2 ) deletes value 89
• unset( arr ) deletes whole array arr

20
PHP arrays Aggregate printing

• arr array( 56, 67, 3gt89 )
• print_r( arr ) aggregate printing
• Array( 0gt56 1gt67 3gt89 )
• reindex the array
• changedIndexes array_values( arr )
• print_r( changedIndexes )
• Array( 0gt56 1gt67 2gt89 )
• original array unchanged
• works even if keys are strings

21
PHP objects

• Object instance of a class
• A class is a collection of variables and
  functions working with these variables. A class
  is defined using the following syntax
• class Cart // C, Java like syntax
•    var items  // member variable
•   function foo( articleNumber, number)
•        // some code   // more
  code here

22
PHP resource

• A resource is a special variable, holding a
  reference to an external resource. Resources are
  created and used by special functions
• As resource types hold special handlers to open
  files, database connections,

23
PHP NULL

• Only one value
• Case insensitive keyword NULL
• Represents that a variable has no value
• a NULL
• Function is_null ? returns true if variable is
  null
• if (is_null( a ) )

24
PHP NULL

• A variable is considered NULL if
• It has been assigned the constant NULL, or
• It has not been set to any value yet, or
• It has been unset()