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Arrays. C SCI 116. Variables. $animals = " ostrich" ; $ animals = " anteater"; $animals = " orangutan"; $animals = " cheetah"; $animals = " hyena"; . What does $animals contain?. Arrays. “ostrich” “anteater” “orangutan” “cheetah” “hyena” . $animals[] .

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arrays

Arrays

C SCI 116

variables
Variables

$animals = "ostrich";

$animals = "anteater";

$animals = "orangutan";

$animals = "cheetah";

$animals = "hyena";

What does $animals contain?

arrays1
Arrays

“ostrich”

“anteater”

“orangutan”

“cheetah”

“hyena”

$animals[]

$animals[] = "ostrich";

$animals[] = "anteater";

$animals[] = "orangutan";

$animals[] = "cheetah";

$animals[] = "hyena";

An array contains a set of data represented by a single variable name

A “list” of values

declaring and initializing indexed arrays
Declaring and Initializing Indexed Arrays
  • An element refers to a piece of data stored in an array
  • An index is an element’s numeric position within the array
    • By default, indexes start with zero (0)
    • An array element is referenced by enclosing its index in brackets after the array name:

print $animals[0];

predefined arrays
Predefined Arrays
  • PHP has a number of built-in arrays
  • Example: $_SERVER
  • Also called autoglobalarrays
    • $_SERVER
    • $_POST
    • $_GET
    • $_COOKIE
    • $_SESSION
printing arrays
Printing Arrays

<?php

print_r($_SERVER);

?>

Much prettier

<?php

print "<pre>";

print_r($_SERVER);

print "</pre>";

?>

Use print_rto quickly display array contents

Not useful for user output

creating an array revisited
Creating an Array: Revisited
  • $animals = array("ostrich", "anteater", "orangutan", "cheetah", "hyena");

– OR –

  • $animals[] = "ostrich";
  • $animals[] = "anteater";
  • $animals[] = "orangutan";
  • $animals[] = "cheetah";
  • $animals[] = "hyena";

$array_name = array(values);

looping through an array
Looping through an Array

ostrich

anteater

orangutan

cheetah

hyena

for ($i=0; $i<sizeof($animals); $i++)

{

print $animals[$i] . "<br>";

//print "{$animals[$i]}<br>";

}

foreach loops
foreachLoops
  • Used to loop through the elements in an array
  • Does not require a counter
  • Syntax:

foreach ($array_name as $variable_name)

{

statements;

}

foreach example
foreach Example

foreach($animals as $animal)

{

print "$animal<br>";

}

practice
Practice

Create an array called $names that contains the names of 5 of your classmates

Print the array using print_r

Print the first name in the array

Print the last name in the array

Print the array using a for loop

Print the array using a for-each loop

associative arrays
Associative Arrays
  • With associative arrays, you specify an element’s key by using the array operator (=>)
  • Syntax :

$array_name = array(key=>value, ...);

PHP Programming with MySQL

associative arrays1
Associative Arrays

$capitals = array("Texas" => "Austen", "Oregon" => "Salem", "Ohio" => "Columbus", "New York" => "Albany");

print "The capital of Texas is " . $capitals['Texas'];

print "The capital of Texas is {$capitals['Texas']}";

The capital of Texas is Austen

PHP Programming with MySQL

associative arrays2
Associative Arrays

$capitals = array("Texas" => "Austen", "Oregon" => "Salem", "Ohio" => "Columbus", "New York" => "Albany");

foreach ($capitals as $state => $capital)

{

print "The capital of $state is $capital.<br>";

}

The capital of Texas is Austen.

The capital of Oregon is Salem.

The capital of Ohio is Columbus.

The capital of New York is Albany.

PHP Programming with MySQL

count or sizeof
count() or sizeof()
  • Use count()or sizeof() to find the total number of elements in an array

$capitals = array("Texas" => "Austen", "Oregon" => "Portland", "Ohio" => "Columbus", "New York" => "Albany");

echo "There are " . count($capitals) . " capitals.";

There are 4 capitals.

converting strings to arrays
Converting Strings to Arrays
  • Use the explode() function to convert a string to an array
  • $array = explode(separators, string);
  • If the string does not contain the specified separators, the entire string is assigned to the first element of the array

ostrich

anteater

orangutan

cheetah

hyena

$animals = "ostrich,anteater,

orangutan,cheetah,hyena";

$animal_array= explode(",", $animals);

foreach ($animal_array as $animal)

echo "$animal<br>";

converting arrays to strings
Converting Arrays to Strings
  • Use the implode() function to convert an array to a string
  • $variable = implode(separators, array);
  • If the string does not contain the specified separators, the entire string is assigned to the first element of the array

$presArray= array("George W. Bush", "William Clinton",

"George H.W. Bush", "Ronald Reagan", "Jimmy Carter");

$presidents = implode(", ", $presArray);

echo $presidents;

removing duplicates
Removing Duplicates
  • The array_unique() function removes duplicate elements from an array
    • Pass the array name

PHP Programming with MySQL

array unique
array_unique()

$topGolfers= array(

"Tiger Woods", "Tiger Woods", "Vijay Singh”, "Vijay Singh", "Ernie Els", "Phil Mickelson",

"Retief Goosen", "Retief Goosen",

"Padraig Harrington", "David Toms",

"Sergio Garcia", "Adam Scott",

"Stewart Cink");

echo "The world's top golfers are:<p>”;

$topGolfers= array_unique($topGolfers);

foreach($topGolfersas $golfer)

{

echo "$golfer<br>";

}

echo "</p>";

PHP Programming with MySQL

determining if a value exists
Determining if a Value Exists
  • in_array()returns Boolean TRUE if a given value exists in an array
  • array_search()determines whether a given value exists in an array and
    • Returns the index or key of the first matching element if the value exists, or
    • Returns false if the value does not exist

if (in_array(“Neurology”, $hospitalDepts))

{

echo "The hospital has a Neurology department.";

}

PHP Programming with MySQL

determining if a key exists
Determining if a Key Exists
  • array_key_existsdetermines whether a given index or key exists
  • array_key_exists($search_key, $array)

$GamePieces["Dancer"] = "Daryl";

$GamePieces["Fat Man"] = "Dennis";

$GamePieces["Assassin"] = "Jennifer";

if (array_key_exists("Fat Man", $GamePieces))

{

echo "{$GamePieces["Fat Man"]} is 'Fat Man'.";

}

PHP Programming with MySQL

sorting arrays
Sorting Arrays
  • The most commonly used array sorting functions are:
    • sort() and rsort() for indexed arrays
    • ksort() and krsort() for associative arrays

PHP Programming with MySQL

slide23

sort()

rsort()

PHP Programming with MySQL

practice1
Practice

Display your $names array in alphabetical order

Display your $names array in reverse alphabetical order

combining arrays
Combining Arrays
  • To merge two or more arrays use the array_merge() function
  • Syntax:

new_array= array_merge($array1, $array2, $array3, ...);

PHP Programming with MySQL

combining arrays continued
Combining Arrays (continued)

$mammals = array("cat", "dog", "bear");

$reptiles = array("snake", "lizard");

$birds = array("emu", "parakeet", "canary");

$animals = array_merge($mammals, $reptiles, $birds);

print_r($animals);

Array ( [0] => cat

[1] => dog

[2] => bear

[3] => snake

[4] => lizard

[5] => emu

[6] => parakeet

[7] => canary )

PHP Programming with MySQL

practice2
Practice

Create a second array called $family_names.

Add at least three names to the array.

Merge $names and $family_namesinto an array called $all_names.

Remove any duplicates from $all_names.

Print $all_names.