PHP Associative Arrays

An associative array in PHP is a special array where each item has a name or label instead of just a number. Usually, arrays use numbers to find things.

• For example, the first item is at position 0, the second is 1, and so on.
• But in an associative array, we use words or names to find things.
• These names are called keys.
• For example, instead of saying "give me the item at position 0," we say "give me the item with the name ‘name’" or "the item with the name ‘age’."

How to Create an Associative Array in PHP?

To create an associative array in PHP, we use the array() function or the short [] syntax, and assign keys to values using the => operator.

$array = array(
    "key1" => "value1",
    "key2" => "value2",
    "key3" => "value3"
);

Or using short syntax (PHP 5.4+):

$array = [
    "key1" => "value1",
    "key2" => "value2",
    "key3" => "value3"
];

Now, let us understand with the help of the example:

<?php
   $person = [
    "name" => "Anjali",
    "age" => 23,
    "city" => "New York"
];

echo $person["name"] . "\n";
echo $person["age"] . "\n";  
echo $person["city"] . "\n"; 
?>

Anjali
23
New York

Iterating Through an Associative Array

1. Using foreach loop

The easiest way to loop through an associative array is by using the foreach loop. It lets us access both the key and the value in each iteration.

Now, let us understand with the help of the example:

<?php
  $fruits = [
    "apple" => "red",
    "banana" => "yellow",
    "grape" => "purple"
];

foreach ($fruits as $fruit => $color) {
    echo "The color of $fruit is $color.\n";
}
?>

The color of apple is red.
The color of banana is yellow.
The color of grape is purple.

This way, each key ($fruit) and its corresponding value ($color) are available inside the loop.

2. Using for loop with keys Arrays

If you want to use a for loop instead of foreach, you first need to get all the keys using array_keys(). Then you can loop through these keys and access their values.

Now, let us understand with the help of the example:

<?php
 $fruits = [
    "apple" => "red",
    "banana" => "yellow",
    "grape" => "purple"
];

$keys = array_keys($fruits);

for ($i = 0; $i < count($keys); $i++) {
    $fruit = $keys[$i];
    echo "The color of $fruit is " . $fruits[$fruit] . ".\n";
}

?>

The color of apple is red.
The color of banana is yellow.
The color of grape is purple.

Accessing and Modifying Values Using Keys

1. Checking if a Key Exists

Before working with a key, it’s good to check if it exists to avoid errors. You can use array_key_exists() or isset() for this.

Now, let us understand with the help of the example:

<?php
$data = [
    "x" => 100,
    "y" => 200
];

if (array_key_exists("x", $data)) {
    echo "Key 'x' is present in the array.\n";
}

if (isset($data["z"])) {
    echo "Key 'z' is set.\n";
} else {
    echo "Key 'z' does not exist.\n";
}
?>

Key 'x' is present in the array.
Key 'z' does not exist.

2. Removing Elements from an Associative Array

To remove a key-value pair, use the unset() function with the key.

Now, let us understand with the help of the example:

<?php
$items = [
    "first" => "one",
    "second" => "two",
    "third" => "three"
];
unset($items["second"]);
print_r($items);
?>

Array
(
    [first] => one
    [third] => three
)

Useful Built-in Functions for Associative Arrays

PHP provides many built-in functions to work with arrays, including associative arrays. Some useful ones are:

• array_keys($array): Returns all keys of the array.
• array_values($array): Returns all values of the array.
• array_key_exists("key", $array): Checks if a key exists.
• count($array): Returns the number of elements.
• unset($array["key"]): Removes a key-value pair.

When to Use Associative Arrays?

Associative arrays are useful when:

• You want to associate meaningful keys with values (e.g., user info, product details).
• You want to access elements by name instead of by position.
• You want to represent structured data without creating a class or object.

Indexed Arrays vs Associative Arrays

Below is the following difference between the Indexed and Associative Arrays:

Conclusion

Associative Arrays in PHP let us store and access data using meaningful names instead of just numbers. This makes our code easier to read and work with, especially when dealing with related information like user details or product data. By using keys, we can quickly find, update, or remove items. PHP also gives us helpful functions to manage associative arrays smoothly. Overall, associative arrays are a handy way to organize data clearly without needing complex structures.