Arrays

Simply put, an array is a set of values. Before this lesson we dealt with variables when one variable held one value. Arrays let you hold many values in a single variable. Here is an example of a simple PHP array:

$numbers = [1, 8, 10, 4, 2];

You can access array elements by their index, which is a zero-based position of the element in the array:

$numbers = [1, 8, 10, 4, 2];

echo $numbers[0]; # Prints 1
echo $numbers[1]; # Prints 8
echo $numbers[2]; # Prints 10
echo $numbers[3]; # Prints 4
echo $numbers[4]; # Prints 2

You can use count function to get the number of elements in the array:

$numbers = [1, 8, 10, 4, 2];

echo count($numbers); # Prints 5

An array can be empty. You can check if the array is empty with empty function:

$numbers = [1, 2, 3];
$names = [];

if(empty($numbers)) # Not empty, "if" block will be skipped
{
    echo 'There are no numbers';
}

if(empty($names)) # Empty, "if" block will be executed
{
    echo 'There are no names';
}

Examples above are arrays of values. There are also associative arrays. These are arrays of key-value pairs. Let's look at the example:

$days_in_month =
[
    'january'   => 31,
    'february'  => 28,
    'march'     => 31,
    'april'     => 30,
    'may'       => 31,
    'june'      => 30,
    'july'      => 31,
    'august'    => 31,
    'septembed' => 30,
    'october'   => 31,
    'november'  => 30,
    'december'  => 31
];

$month = 'april';

echo 'There are ' . $days_in_month[$month] . ' days in ' . $month;

# Prints "There are 30 days in april"

In the example above a name of a month is a key and a days count is a value. You can get a value by its key.

You can set array values in the same manner:

$numbers = [1, 8, 10, 4, 2];

$days_in_month =
[
    'january'  => 31,
    'february' => 28
];

$numbers[3] = 50;
echo $numbers[3]; # Prints 50

$days_in_month['march'] = 31;
echo $days_in_month['march']; # Prints 31

You can check if there is a value in the associative array at a given key with isset function:

$days_in_month =
[
    'january'  => 31,
    'february' => 28
];

if(isset($days_in_month['march']))
{
    echo $days_in_month['march'];
}
else
{
    echo 'Month not found'; # There is no "march" key so it will print that
}

You can remove a key-value pair from the associative array by the key with unset function:

$days_in_month =
[
    'january'  => 31,
    'february' => 28
];

unset($days_in_month['january']);

var_dump($days_in_month); # Prints the array with the only one key-value pair