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Php Arrays Tutorial


A PHP array is an ordered collection of data. PHP Arrays are very easy to create. PHP Arrays are dynamic - Items can be added and removed at will.

PHP Arrays can be created in two different ways

PHP Arrays using Array Operator []

Array operator [] can be used to create an array in PHP. A general syntaxt of array operator for the creation of an array in PHP is:

$arrayName['key'] = value;

Here we are going to discuss two main types of PHP arrays using array operator - Numeric Arrays & Associative Arrays

PHP Numeric Arrays

Numeric arrays have their elements ordered by numbers (indexes). The first index of a numeric array is always 0.

<?php #arrays.php
   $ar[0] = "Jim";
   $ar[1] = "Bill";
   $ar[2] = "Joe";

   //accessing array elements using a numeric key (index)
   echo $ar[0];   //Jim
   echo $ar[1];   //Bill
   echo $ar[2];   //Joe
?>

PHP Associative Arrays

Associative arrays have their elements indexed with strings.

<?php #arrays.php
   $scores['Jim'] = "32";
   $scores['Bill'] = "30";
   $scores['Joe'] = "35";

   //accessing array elements using a string key 
   echo $scores['Jim'];   //32
   echo $scores['Bill'];   //30
   echo $scores['Joe'];   //35
?>

PHP Arrays using array() Construct

PHP uses array() construct to create an array. The structure of creation of array using array() construct is really simple, simply type array() and it will create an array. A general syntax for array() would be

array(key => value, key => value, key => value)

some examples of php array() constructs are given here

<?php #arrays.php
   array();
   array(1, 222, 33, 55);
   array('price', 'category', 'quantity');
   array(3 => 1, 4 => 453);
   array('a' => 2, 'b' => '33');
   array('a' => 'first data', 'b' => 'second');
?>

Count array elements:

To count the elements of an array you can use the count() function

<?php #arrays.php
//declaring a new array
 $arr = array(1, 2, 3, "a", "b", "c");

//accessing the number of elements
$total = count($arr);
echo "<p>the array has $total elements.</p>"; //the array has 6 elements.
?>

More about Arrays:

<?php #arrays.php
//Creating a simple array of numbers
$myArray = array(1, 3, 4, 5);

//Creating a simple array of strings
$myArray2 = array('cats', 'dogs', 'chickens');

//Arrays can contain items of different types, and even other nested arrays
$myMixedArray = array('monkeys', 5, 3.7, array('a nested array', 'blah'), 'something');

// Array elements are accessed by their index, counting from 0 
echo $myArray2[0]; // Outputs "cats" 
echo $myArray2[2]; // Outputs "chickens"

// Cycling through an array can be achieved using a for loop...
for ($i = 0; $i < count($myArray); $i++) { echo $myArray[$i]; }

// ... or using the special foreach language construct
foreach ($myArray as $item) { echo $item; }

// Creating an indexed array (aka a hash table) is easy:
$indexedArray = array( 'firstname' => 'Simon', 'lastname' => 'Willison', 'age' => 21 );

// Items in an indexed array can be accessed by key:
echo $indexedArray[‘firstname’]; // outputs “Simon”  

// Adding items to the end of an array can be done with:
$myArray[] = ‘something’;  

// Items in an array can be replaced by assignign to their index
$myArray[2] = ‘blah’;

/*An invaluable function for debugging an array is print_r() , which prints out any PHP data
structure (no matter how complex or nested) in a nice human readable format. 
Try the following and see what happens:*/
print_r($_SERVER);
// Prints out the array of server variables ?>

Click here to read about PHP loops


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