To pass an associative array to a function in PHP, declare the function with a parameter to accept an array, access its values using keys, check for key existence to avoid errors, optionally modify the array by reference or return a new version. 1) Declare the function normally, expecting an array; 2) Access array values inside the function using their keys; 3) Use isset() or array_key_exists() before accessing keys to prevent undefined index errors; 4) Pass the array by reference using & if you want modifications to affect the original array; 5) Alternatively, return a modified copy of the array instead of changing it in-place for clarity and immutability.

You can pass an associative array to a PHP function just like any other variable. The key is understanding how to handle it inside the function once it's received.

Declaring the Function to Accept an Associative Array

You don't need to do anything special when defining the function — just set a parameter to accept an array:

function processUserData($user) {
    echo "Name: " . $user['name'] . "<br>";
    echo "Email: " . $user['email'] . "<br>";
}

This function expects an associative array with at least the keys 'name' and 'email'.

When calling it, you simply pass the array:

$userData = [
    'name' => 'Alice',
    'email' => 'alice@example.com'
];

processUserData($userData);

Make sure the array has the expected structure so your function doesn’t run into undefined indexes.

Accessing and Using the Array Inside the Function

Once the array is passed in, you can access its values using the keys:

function showUserInfo($info) {
    if (isset($info['username'])) {
        echo "Username: " . $info['username'] . "<br>";
    }

    if (isset($info['age'])) {
        echo "Age: " . $info['age'] . "<br>";
    }
}

It’s good practice to check if keys exist using isset() or array_key_exists() before accessing them. This avoids errors if someone calls your function with an incomplete or unexpected array.

If you're expecting certain keys every time, you might even want to add checks and throw exceptions or trigger errors when they’re missing.

Modifying the Array Inside the Function

If you want to change the array inside the function and have those changes affect the original array outside, you can pass it by reference:

function updateStatus(&$data) {
    $data['status'] = 'processed';
}

$record = ['id' => 123];
updateStatus($record);

print_r($record); // status will now be 'processed'

Notice the & symbol before the parameter name in the function definition. That tells PHP to pass the array by reference rather than making a copy.

Without the &, any changes made inside the function would only affect the local copy of the array.

Returning Modified Data Instead of Modifying In-Place

Another common approach is to return a new version of the array instead of modifying the original:

function addTimestamp($data) {
    $data['timestamp'] = time();
    return $data;
}

$input = ['id' => 456];
$output = addTimestamp($input);

This makes your code more predictable and easier to debug since the original array stays unchanged unless explicitly replaced by the returned value.

• Use pass-by-reference when performance matters and you're working with large data sets.
• Return a new array for clarity and immutability, especially in smaller functions or libraries.

That’s basically how it works. Passing associative arrays to functions in PHP is straightforward, but handling the keys safely and deciding whether to modify in-place or return a new array makes all the difference.

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