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Creating Arrays
You can create an array using either the array() function or the array operator []. The array() function is usually used when you want to create a new array and populate it with more than one element at the same time. The array operator is used when you want to create a new array with just one element (for now), or when you want to add to an existing element.
The following code snippet shows how to create an array called $rainbow, containing all its various colors:
$rainbow = array("red", "orange", "yellow", "green", "blue", "indigo", "violet");
The following snippet shows the same array being created incrementally using the array operator:
$rainbow[] = "red";
$rainbow[] = "orange";
$rainbow[] = "yellow";
$rainbow[] = "green";
$rainbow[] = "blue";
$rainbow[] = "indigo";
$rainbow[] = "violet";
Both snippets create a seven-element array called $rainbow, with values starting at index position 0 and ending at index position 6. If you wanted to be literal about it, you could have specified the index positions, such as in this code:
$rainbow[0] = "red";
$rainbow[1] = "orange";
$rainbow[2] = "yellow";
$rainbow[3] = "green";
$rainbow[4] = "blue";
$rainbow[5] = "indigo";
$rainbow[6] = "violet";
However, PHP does this for you when positions are not specified, and that eliminates the possibility that you will misnumber your elements, as in this example:
$rainbow[0] = "red";
$rainbow[1] = "orange";
$rainbow[2] = "yellow";
$rainbow[5] = "green";
$rainbow[6] = "blue";
$rainbow[7] = "indigo";
$rainbow[8] = "violet";
Regardless of whether you initially create your array with the array() function or the array operator, you can still add to it using the array operator:
$rainbow = array("red", "orange", "yellow", "green", "blue", "indigo");
$rainbow[] = "violet";
The examples used in this section were of numerically indexed arrays, arguably the most common type you''ll see. In the next two sections, you learn about two other types of arrays: associative and multidimensional.
Creating Associative Arrays
Whereas numerically indexed arrays use an index position as the key0, 1, 2, and so forthassociative arrays utilize actual named keys. The following example demonstrates this by creating an array called $character with four elements:
$character = array(
"name" => "Bob",
"occupation" => "superhero",
"age" => 30,
"special power" => "x-ray vision"
);
The four keys in the $character array are called name, occupation, age, and special power. The associated values are Bob, superhero, 30, and x-ray vision. You can reference specific elements of an associative array using the specific key, such as in this example:
<?php
echo $character[''occupation''];
?>
The output of this snippet is this:
superhero
As with numerically indexed arrays, you can use the array operator to add to an associative array:
$character[''supername''] = "Mega X-Ray Guy";
This example adds a key called supername with a value of Mega X-Ray Guy.
Creating Multidimensional Arrays
The first two types of arrays hold strings and integers, whereas this third type holds other arrays. If each set of key/value pairs constitutes a dimension, a multidimensional array holds more than one series of these key/value pairs. For example, Listing 7.1 defines a multidimensional array called $characters, each element of which contains an associative array.
Listing 7.1 Defining a Multidimensional Array
1: <?php
2: $characters = array(
3: array(
4: "name" => "Bob",
5: "occupation" => "superhero",
6: "age" => 30,
7: "special power" => "x-ray vision"
8: ),
9: array(
10: "name" => "Sally",
11: "occupation" => "superhero",
12: "age" => 24,
13: "special power" => "superhuman strength"
14: ),
15: array(
16: "name" => "Jane",
17: "occupation" => "arch villain",
18: "age" => 45,
19: "special power" => "nanotechnology"
20: )
21: );
22: ?>
In line 2, the $characters array is initialized using the array() function. Lines 38 represent the first element, lines 914 represent the second element, and lines15?20 represent the third element. These elements can be referenced as $characters[0], $characters[1], and $characters[2].
However, if you attempt to print these elements:
<?php
echo $character[2];
?>
the output will be this:
Array
To access specific information found within the array element, you need to access the element index position and the associative name of the value you want to view. Take a look at this example:
<?php
echo $character[2][''occupation''];
?>
It will print this:
superhero
