PHP Arrays

What is array in PHP

Arrays in PHP is a type of data structure that allows us to store multiple elements of similar data type under a single variable thereby saving us the effort of creating a different variable for every data.

An array stores multiple values in one single variable.

<?php
$cars = array("Volvo", "BMW", "Toyota");
echo "I like " . $cars[0] . ", " . $cars[1] . " and " . $cars[2] . ".";
?>

An array can hold many values under a single name, and you can access the values by referring to an index number.

How to Create an Array in PHP

In PHP, the array() function is used to create an array:

array();

Types of Array in PHP

In PHP, there are three types of arrays:

• Indexed arrays – Arrays with a numeric index
• Associative arrays – Arrays with named keys
• Multidimensional arrays – Arrays containing one or more arrays

PHP Indexed Arrays

There are two ways to create indexed arrays:

The index can be assigned automatically (index always starts at 0), like this:

$cars = array("Volvo", "BMW", "Toyota");

or the index can be assigned manually:

$cars[0] = "Volvo";
$cars[1] = "BMW";
$cars[2] = "Toyota";

The following example creates an indexed array named $cars, assigns three elements to it, and then prints a text containing the array values:

<?php
$cars = array("Volvo", "BMW", "Toyota");
echo "I like " . $cars[0] . ", " . $cars[1] . " and " . $cars[2] . ".";
?>

Loop Through an Indexed Array

To loop through and print all the values of an indexed array, you could use a for loop, like this:

<?php
$cars = array("Volvo","BMW","TOYOTA");
$arrlength = count($cars);
for($x = 0; x < arrlength; x++){
echo $cars[$x];
echo "<br>";
}
?>

PHP Associative Arrays

Associative arrays are arrays that use named keys that you assign to them.

There are two ways to create an associative array: 

$age = array("Peter"=>"35", "Ben"=>"37", "Joe"=>"43");

or:

$age['Peter'] = "35";
$age['Ben'] = "37";
$age['Joe'] = "43";

The named keys can then be used in a script:

<?php
$age = array("Peter"=>"35", "Ben"=>"37", "Joe"=>"43");
echo "Peter is " . $age['Peter'] . " years old.";
?>

Loop Through an Associative Array

To loop through and print all the values of an associative array, you could use a foreach loop, like this:

<?php
$age = array("Peter"=>"35", "Ben"=>"37", "Joe"=>"43");

foreach($age as $x => $x_value) {
  echo "Key=" . $x . ", Value=" . $x_value;
  echo "<br>";
}
?>

PHP Multidimensional Arrays

In the previous sections, we have described associative arrays that are a single list of key/value pairs.

However, sometimes you want to store values with more than one key. For this, we have multidimensional arrays.

A multidimensional array is an array containing one or more arrays.

PHP supports multidimensional arrays that are two, three, four, five, or more levels deep. However, arrays more than three levels deep are hard to manage for most people.

The dimension of an array indicates the number of indices you need to select an element.

• For a two-dimensional array you need two indices to select an element
• For a three-dimensional array you need three indices to select an element

PHP – Two-dimensional Arrays

A two-dimensional array is an array of arrays (a three-dimensional array is an array of arrays of arrays).

First, take a look at the following table:

Name	Stock	Sold
Volvo	22	18
BMW	15	13
Saab	5	2
Land Rover	17	15

We can store the data from the table above in a two-dimensional array, like this:

$cars = array (
  array("Volvo",22,18),
  array("BMW",15,13),
  array("Saab",5,2),
  array("Land Rover",17,15)
);

Now the two-dimensional $cars array contains four arrays, and it has two indices: row and column.

To get access to the elements of the $cars array we must point to the two indices (row and column):

<?php
echo $cars[0][0].": In stock: ".$cars[0][1].", sold: ".$cars[0][2].".<br>";
echo $cars[1][0].": In stock: ".$cars[1][1].", sold: ".$cars[1][2].".<br>";
echo $cars[2][0].": In stock: ".$cars[2][1].", sold: ".$cars[2][2].".<br>";
echo $cars[3][0].": In stock: ".$cars[3][1].", sold: ".$cars[3][2].".<br>";
?>

We can also put a for loop inside another for loop to get the elements of the $cars array (we still have to point to the two indices):

<?php
for ($row = 0; $row < 4; $row++) {
  echo "<p><b>Row number $row</b></p>";
  echo "<ul>";
  for ($col = 0; $col < 3; $col++) {
    echo "<li>".$cars[$row][$col]."</li>";
  }
  echo "</ul>";
}
?>