PHP Arrays

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PHP Arrays User-Defined Functions
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What are Arrays?

• An array in PHP is actually an ordered map. A
  map is a type that maps values to keys. This type
  is optimized in several ways, so 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. Because you can have another PHP array as a
  value, you can also quite easily simulate trees.

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Array Types

• There are differing opinions on whether PHP
  'really' supports different array types. The book
  says 'yes', defining them as Indexed and
  Associative Arrays, based on whether the key is
  numeric or string.
• PHP.net says "There are no different indexed and
  associative array types in PHP there is only one
  array type, which can both contain integer and
  string indices.
• It's common to refer to them like the book.

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So What's a Key?

• An array key can be thought of as the address or
  reference to a specific value contained within an
  array.
• A key can be an integer or a string
• Floats used as keys are truncated to integers
• If you don't specify a key, the array key will
  automatically start with 0 (zero) and auto
  increment by 1 each time a new value is entered
  into the array.
• Key must be unique.

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Creating an Array

• An array can be created by the array()
  language-construct. It takes a number of
  comma-separated key value pairs.
• colors array('red''rojo',
• 'green''verde',
• 'blue''azul')

value
key
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Accessing Array Values

• Array values can be accessed a number of ways.
  Most directly, arrays can be output using print()
  and echo. However, you have to indicate the key
  of the value you wish to print, otherwise the
  output will just be "Array".
• Examples follow

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Example 1

• Create an array with numeric keys, automatically
  created starting at zero
• colors array('red',
• 'green',
• 'blue')
• echo colors1 //green
• echo colors //Array
• echo colors0 //red

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Example 2

• Create an array with numeric with keys starting
  at 1, then incremented automatically by 1
• colors array(1'red',
• 'green',
• 'blue')
• echo colors1 //red
• echo colors3 //blue
• echo colors0 //Notice Undefined

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Example 3

• Create an array with string keys
• colors array('red''rojo',
• 'green''verde',
• 'blue''azul')
• echo colors'blue' //azul
• echo colors'red' //rojo
• echo colors0 //Notice Undefined

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Quickly View Array Structure

• You can quickly view the keys and values of an
  array using print_r()
• colors array('red',
• 'green',
• 'blue')
• print ""
• print_r(colors)
• print ""

Array ( 0 red 1 green 2
blue )
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Even More Detail

• You can quickly view the structure, keys and
  values of an array using var_dump()
• colors array('red',
• 'green',
• 'blue')
• print ""
• var_dump(colors)
• print ""

array(3) 0 string(3) "red" 1
string(5) "green" 2 string(4) "blue"
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Add Items to an Array

• After an array has been created, you can add
  values to the 'end' of the array
• colors 'orange'
• print ""
• print_r(colors)
• print ""

Array ( 0 red 1 green 2
blue 3 orange )
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Be Careful!

• Using the wrong syntax when adding values to your
  array can overwrite your array
• colors "turquoise" will overwrite the entire
  array with the value of "turquoise".
• Proper syntax for adding a value to an array is
• colors "turquoise" or
• colors5 "turquoise"

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Delete Array Element

• After an array has been created, you can add
  values to the 'end' of the array
• unset(colors2)
• print ""
• print_r(colors)
• print ""

Array ( 0 red 1 green 3
orange )
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Merge Arrays

• Combine arrays
• colors array('red',
• 'green',
• 'blue')
• others array('purple',
• 'pink')
• all array_merge(colors,others)

Array ( 0 red 1 green 2
blue 3 purple 4 pink )
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Count

• You can count the number of values in an array
• numColors count (colors)

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Delete or Reset Array

• Delete an array
• unset(colors)
• Reset an array (delete all keys and values but
  keep array)
• colors array()

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foreach Loops

• foreach loops are great way to access the values
  in an array.
• colors array('red',
• 'green',
• 'blue')
• foreach(colors as keyval)
• echo "Key key is val"

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Transform Arrays to Strings

• Let's take our colors and transform them into a
  string with
  at the end of each color
• newString implode('
  ',colors)

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Transform Strings to Arrays

• Let's take our colors and transform them into a
  string with
  at the end of each color
• names "Bob, Terry, Carl"
• guysArray explode(', ', names)
• print ""
• print_r(guysArray)
• print ""

Array ( 0 Bob 1 Terry 2
Carl )
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Sorting Arrays

• Arrays can be sorted by key or value
• You can sort and keep keys aligned, or sort
  values and have new keys assigned.

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sort() Function

• sort() is alphabetical if values are strings, or
  numeric if values are numeric.
• colors array('red',
• 'green',
• 'blue')
• sort(colors)
• print_r(colors)

Array ( 0 blue 1 green 2
red )
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rsort() Function

• rsort() sorts in reverse
• colors array('green',
• 'red',
• 'blue')
• rsort(colors)
• print_r(colors)

Array ( 0 red 1 green 2
blue )
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ksort() Function

• ksort() sorts keys, keeping values correlated to
  keys
• colors array('green',
• 'red',
• 'blue')
• ksort(colors)
• print_r(colors)

Array ( 0 green 1 red 2
blue )
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shuffle() Function

• shuffle() randomly reorganizes the order of the
  array and regens the keys
• colors array('green',
• 'red',
• 'blue')
• shuffle(colors)
• print_r(colors)

Array ( 0 blue 1 red 2
green )
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extract() Function

• Use extract() to automatically create variables
  from an array, where the variables created are
  the keys and their values are the associated
  array values
• volume array ('can''16 oz',
• 'bottle''12 oz',
• 'gulp''32 oz')
• extract(volume)
• echo can // 16 oz
• echo bottle // 12 oz
• echo gulp // 32 oz

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array_search() Function

• array_search() searches the array for a given
  value and returns the corresponding key if
  successful.
• array array(0 'blue', 1 'red', 2
  'green', 3 'red')
• key array_search('green', array)
• // key 2
• key array_search('red', array) 
• // key 1
• Also see array functions
• array_key_exists(key, array) return (T, F)
• In_array(element, array) return (T, F)

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Multidimensional Arrays

• Arrays can contain other arrays.
• fruits array('apples',
• 'bananas',
• 'oranges')
• meats array('steaks',
• 'hamburgers',
• 'hotdogs')
• groceries array('Fruit'fruits,
• 'Meat'meats)

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Multidimensional Arrays

• Array
• (
• Fruit Array
• (
• 0 apples
• 1 bananas
• 2 oranges
• )
• Meat Array
• (
• 0 steaks
• 1 hamburgers
• 2 hotdogs
• )
• )

groceries'Meat''2' // hotdogs
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PHP functions
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PHP functions

• standard functions
• arrays, date and time, files and directories,
  http, maths, strings, etc...
• programmer-defined functions
• untyped parameters
• may or may not return a value or a reference
• unusual effect on variable scope
• can set default parameters
• can set variable parameters

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defining functions
result string1.string2 return
result s1 Gandalf s2 the
Grey echo strconcat (s1, s2) ?
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variable scope in functions
function weirdScope () a 2 // a is
local a 3 weirdScope () echo a //prints
3
function weirdScope () global a a 2
a 3 weirdScope () echo a // prints 5
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Example

• colors array('red','blue','green')
• places array('New York','Denver','Chicago')
• function makePulldown(fieldName, data)
• echo "\n"
• foreach(data as key value)
• echo "
• value
• \n"
• echo "\n"
• // end function
• makePulldown('favColors',colors)
• makePulldown('favPlaces',places)

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default parameters

• specify default parameters in the function
  declaration
• default value can be a constant, but not a
  complex expression
• any number of default parameters can be defined
• parameters with default values must be listed
  after parameters without default values in the
  function definition

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default parameters
function order (flavour vanilla, n 1)
switch (flavour) case vanilla
price n priceOf vanilla break
default echo Sorry, out of stock.
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Returning Values

• Previous function examples simply output to the
  browser. A function can also return a value,
  which can then be further processed.
• function calcTax(amount, rate .074)
• return amount rate
• // end function
• amt 125.00
• tax calcTax(amt, .093)
• tax number_format(tax,2)
• total amt tax
• echo "Sub Total amt
  
• Tax tax
  
• Total total
  "

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variable parameters

• if no parameters are declared for a function, you
  can still pass multiple parameters
• access to undeclared parameters is available
  through special PHP functions
• func_get_args ()
• func_num_args ()
• func_get_arg (argName)

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variable parameters
function countList () if (func_num_args ()
0) return false else for
(i 0 i count func_get_arg (i)