Working With Arrays in PHP

Arrays are common to many programming languages. They are special variables which can hold more than one value, each stored in its own numbered 'space' in the array. Instead of having many similar variables, you can store the data as elements in an array.Each element in the array has its own ID so that it can be easily accessed.

There are three different kind of arrays:

• Numeric array - An array with a numeric ID key
• Associative array - An array where each ID key is associated with a value
• Multidimensional array - An array containing one or more arrays

Numeric Arrays

A numeric array stores each element with a numeric ID key. There are different ways to create a numeric array.

Example 1

In this example the ID key is automatically assigned:

Code:

$names = array("John","Paul","Steve");

Example 2

In this example we assign the ID key manually:

Code:

$names[0] = "John";
$names[1] = "Paul";
$names[2] = "Steve";

The ID keys can be used in a script in the following way

Code:

<?php
$names[0] = "John";
$names[1] = "Paul";
$names[2] = "Steve";
echo $names[1] . " and " . $names[2] . 
" are ". $names[0] . "'s Friends";
?>

The code above will output:

Paul and Steve are John's Friends

Associative Arrays

An associative array, each ID key is associated with a value.When storing data about specific named values, a numerical array is not always the best way to do it.With associative arrays we can use the values as keys and assign values to them.

Example 1

In this example we use an array to assign ages to the different persons:

$ages = array("John"=>32, "Paul"=>30, "Steve"=>34);

Example 2

This example is the same as example 1, but shows a different way of creating the array:

Code:

$ages['John'] = "32";
$ages['Paul'] = "30";
$ages['Steve'] = "34";

The ID keys can be used in a script:

Code:

<?php
$ages['John'] = "32";
$ages['Paul'] = "30";
$ages['Steve'] = "34";
echo "John is " . $ages['John'] . " years old.";
?>

The code above will output:

John is 32 years old.

Multidimensional Arrays

In a multidimensional array, each element in the main array can also be an array. And each element in the sub-array can be an array, and so on.

Example

In this example we create a multidimensional array, with automatically assigned ID keys:

Code:

$families = array
(
  "Griffin"=>array
  (
  "John",
  "Lois",
  "Megan"
  ),
  "Paul"=>array
  (
  "Glenn"
  ),
  "Brown"=>array
  (
  "Cleveland",
  "Loretta",
  "Junior"
  )
);

The array above would look like this if written to the output when done through print_r function:

Code:

Array
(
[Griffin] => Array
  (
  [0] => John
  [1] => Lois
  [2] => Megan
  )
[Paul] => Array
  (
  [0] => Glenn
  )
[Brown] => Array
  (
  [0] => Cleveland
  [1] => Loretta
  [2] => Junior
  )
)