Associative Arrays

PHP doesn't have a separate dictionary or map type — an array with string keys instead of numeric ones is the associative array, using the exact same square-bracket syntax you already know.

Creating one

<?php
$person = [
    "name" => "Jamie",
    "age" => 34,
    "city" => "Austin"
];

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

Jamie
34

=> pairs a key with its value. Every array in PHP, whether it looks "indexed" or "associative," is really the same ordered map type internally — an indexed array is just one whose keys happen to be sequential integers starting at 0.

Adding, updating, and checking keys

<?php
$person = ["name" => "Jamie", "age" => 34];

$person["email"] = "jamie@example.com";
$person["age"] = 35;

var_dump(isset($person["email"]));
var_dump(isset($person["phone"]));
var_dump(array_key_exists("age", $person));

print_r($person);
?>

bool(true)
bool(false)
bool(true)
Array
(
    [name] => Jamie
    [age] => 35
    [email] => jamie@example.com
)

Assigning to an existing key overwrites its value; assigning to a new key adds it, appended at the end. isset() is the standard way to check whether a key exists without triggering a warning for a missing one — reading $person["phone"] directly when it isn't set would produce a warning rather than a clean false.

Looping with key and value together

The two-variable form of foreach gives you both the key and the value on each pass — this is how you'll iterate over associative arrays almost every time:

<?php
$prices = ["coffee" => 4.5, "tea" => 3.0, "juice" => 5.25];

foreach ($prices as $item => $price) {
    echo ucfirst($item) . ": \$" . $price . "\n";
}
?>

Coffee: $4.5
Tea: $3
Juice: $5.25

foreach ($prices as $item => $price) destructures each pair as it goes. ucfirst() capitalizes just the first letter of a string, handy for turning a lowercase key into something presentable.