Associative Arrays

Arrays may have non-numeric indexes.

Inserting Data

Data can be inserted by specifying certain key and value.

Example:

$scores = []; $scores["Smith"] = 89; $scores["Alex"] = 85;

In this example, 2 records have been inserted.

Accessing Values

Values can be accessed via their keys.

Let's look at the following example:

<?php $drinks = []; $drinks["Coke"] = 1.55; $drinks["Water"] = 0.80; echo $drinks["Coke"];

Output:

1.55

The key-value pair for Coke is set at line 4 and accessed at line 7.

Not Set Key

Accessing key that's not set in the array results in warning and null value.

Let's look at the following example:

<?php $drinks = []; $drinks["Orange Juice"] = 1.55; $drinks["Water"] = 0.80; if($drinks["Coke"] === null) { echo 'Not set'; }

Output:

Notice: Undefined index: Coke in index.php on line 7 Not set

The array doesn't contain any Coke key, so $drinks["Coke"] has a value of null.

Iterating Elements

Let's have a program in which students scores are stored in array and printed afterwards.

<?php $scores = []; $scores["Smith"] = 89; $scores["Alex"] = 75; $scores["John"] = 87; foreach($scores as $key => $value) { echo $key . " " . $value; echo "<br>"; }

Output:

Smith 89 Alex 75 John 87

Removing Elements

That's done via the unset function like in this example:

<?php $drinks = []; $drinks['Coke'] = 1.65; unset($drinks['Coke']);

Checking if key exists

It can be done via the isset function like in the following code:

<?php $drinks = []; $drinks['Juice'] = 1.58; if(isset($drinks['Juice'])) { echo 'Juice'; } if(isset($drinks['Water'])) { echo 'Water'; }

Output:

Juice

Water key is not set thus Water is not printed.

Size

Size is the count of the key-value pairs.

It can be accessed via the count function.

Let's look at this example:

<?php $drinks["Coke"] = 1.50; $drinks["Orange Juice"] =2.30; $drinks["Water"] = 0.80; $drinks["Apple Juice"] = 2.35; unset($drinks["Coke"]); echo count($drinks);

Output:

3

4 records were inserted and 1 is deleted afterwards. This makes for 3 key-value pairs.