Compound Data Structures in PHP: Nested Arrays and Associative Arrays

Introduction

Welcome to our exploration of Nested Data Structures in PHP . After understanding the basics of PHP arrays, we'll delve into nested associative arrays and multidimensional arrays. These structures enable us to handle complex and hierarchical data, which is typical in real-world scenarios. This lesson will guide you through a recap of the basics, the creation and modification of nested arrays, as well as common operations.

Recap: Associative Arrays, Indexed Arrays, and Understanding Nested Structures

As a quick recap, PHP associative arrays store key-value pairs, and indexed arrays store elements in a linear fashion with numeric indices. These structures can be nested. Here's a simple example of a school directory using associative arrays: PHP<?php // Associative array with grades as keys and arrays of students as values $school_directory = array( "Grade1" => array("Amy", "Bobby", "Charlie"), "Grade2" => array("David", "Eve", "Frank"), "Grade3" => array("George", "Hannah", "Ivy") ); // Prints the Grade1 list in the associative array foreach ($school_directory["Grade1"] as $student) { echo $student . " "; } // Output: Amy Bobby Charlie ?>

Creating Nested Associative and Indexed Arrays

Just like their non-nested versions, creating nested structures in PHP is straightforward. Nested Associative Array: PHP<?php // Associative array within an associative array $nested_map = array( "fruit" => array( "apple" => "red", "banana" => "yellow" ), "vegetable" => array( "carrot" => "orange", "spinach" => "green" ) ); // Prints the nested associative array foreach ($nested_map as $category => $items) { echo $category . ": "; foreach ($items as $item => $color) { echo $item . "(" . $color . ") "; } echo "\n"; } ?> Nested Indexed Array: PHP<?php // Arrays within an array $nested_array = array( array(1, 2, 3), array(4, 5, 6), array(7, 8, 9) ); // Prints the nested array foreach ($nested_array as $arr) { foreach ($arr as $val) { echo $val . " "; } echo "\n"; } ?> Nested Associative and Indexed Arrays: PHP<?php // Arrays within an associative array $map_of_arrays = array( "numbers" => array(1, 2, 3), "more_numbers" => array(4, 5, 6) ); // Prints the associative array with nested arrays foreach ($map_of_arrays as $key => $array) { echo $key . ": "; foreach ($array as $val) { echo $val . " "; } echo "\n"; } ?>

Join the 1M+ learners on CodeSignal

Be a part of our community of 1M+ users who develop and demonstrate their skills on CodeSignal

PHP

<?php
// Associative array within an associative array
$nested_map = array(
    "fruit" => array(
        "apple" => "red",
        "banana" => "yellow"
    ),
    "vegetable" => array(
        "carrot" => "orange",
        "spinach" => "green"
    )
);

// Prints the nested associative array
foreach ($nested_map as $category => $items) {
    echo $category . ": ";
    foreach ($items as $item => $color) {
        echo $item . "(" . $color . ") ";
    }
    echo "\n";
}
?>

PHP

<?php
// Arrays within an array
$nested_array = array(
    array(1, 2, 3),
    array(4, 5, 6),
    array(7, 8, 9)
);

// Prints the nested array
foreach ($nested_array as $arr) {
    foreach ($arr as $val) {
        echo $val . " ";
    }
    echo "\n";
}
?>

PHP

<?php
// Arrays within an associative array
$map_of_arrays = array(
    "numbers" => array(1, 2, 3),
    "more_numbers" => array(4, 5, 6)
);

// Prints the associative array with nested arrays
foreach ($map_of_arrays as $key => $array) {
    echo $key . ": ";
    foreach ($array as $val) {
        echo $val . " ";
    }
    echo "\n";
}
?>

PHP

<?php
// Associative array within an associative array
$nested_map = array(
    "fruit" => array(
        "apple" => "red",
        "banana" => "yellow"
    ),
    "vegetable" => array(
        "carrot" => "orange",
        "spinach" => "green"
    )
);

// Accessing apple's color from nested associative array
echo $nested_map["fruit"]["apple"]; // Output: red
?>

<?php
// Associative array within an associative array
$nested_map = array(
    "fruit" => array(
        "apple" => "red",
        "banana" => "yellow"
    ),
    "vegetable" => array(
        "carrot" => "orange",
        "spinach" => "green"
    )
);

// Accessing apple's color from nested associative array
echo $nested_map["fruit"]["apple"]; // Output: red
?>

PHP

<?php
// Arrays within an array
$nested_array = array(
    array(1, 2, 3),
    array(4, 5, 6),
    array(7, 8, 9)
);

// Accessing the 3rd value from the 2nd array in nested indexed array
echo $nested_array[1][2]; // Output: 6
?>

<?php
// Arrays within an array
$nested_array = array(
    array(1, 2, 3),
    array(4, 5, 6),
    array(7, 8, 9)
);

// Accessing the 3rd value from the 2nd array in nested indexed array
echo $nested_array[1][2]; // Output: 6
?>

PHP

<?php
// Arrays within an associative array
$map_of_arrays = array(
    "numbers" => array(1, 2, 3),
    "more_numbers" => array(4, 5, 6)
);

// Accessing the second value from the 'numbers' array in map_of_arrays
echo $map_of_arrays["numbers"][1]; // Output: 2
?>

<?php
// Arrays within an associative array
$map_of_arrays = array(
    "numbers" => array(1, 2, 3),
    "more_numbers" => array(4, 5, 6)
);

// Accessing the second value from the 'numbers' array in map_of_arrays
echo $map_of_arrays["numbers"][1]; // Output: 2
?>

PHP

<?php
// Associative array within an associative array
$nested_map = array(
    "fruit" => array(
        "apple" => "red", 
        "banana" => "yellow"
    ),
    "vegetable" => array(
        "carrot" => "orange",
        "spinach" => "green"
    )
);

// Modifying spinach's color to red
$nested_map["vegetable"]["spinach"] = "red";

// Adding cherry to the 'fruit' map in nested_map
$nested_map["fruit"]["cherry"] = "red";

// Deleting apple from the 'fruit' map in nested_map
unset($nested_map["fruit"]["apple"]);
?>

<?php
// Associative array within an associative array
$nested_map = array(
    "fruit" => array(
        "apple" => "red", 
        "banana" => "yellow"
    ),
    "vegetable" => array(
        "carrot" => "orange",
        "spinach" => "green"
    )
);

// Modifying spinach's color to red
$nested_map["vegetable"]["spinach"] = "red";

// Adding cherry to the 'fruit' map in nested_map
$nested_map["fruit"]["cherry"] = "red";

// Deleting apple from the 'fruit' map in nested_map
unset($nested_map["fruit"]["apple"]);
?>

PHP

<?php
// Arrays within an array
$nested_array = array(
    array(1, 2, 3),
    array(4, 5, 6),
    array(7, 8, 9)
);

// Adding 10 to the first array in nested array
$nested_array[0][] = 10;

// Deleting the 2nd value from the 3rd array in nested array
unset($nested_array[2][1]);
?>

<?php
// Arrays within an array
$nested_array = array(
    array(1, 2, 3),
    array(4, 5, 6),
    array(7, 8, 9)
);

// Adding 10 to the first array in nested array
$nested_array[0][] = 10;

// Deleting the 2nd value from the 3rd array in nested array
unset($nested_array[2][1]);
?>

PHP

<?php
// Associative array within an associative array
$nested_map = array(
    "fruit" => array(
        "apple" => "red",
        "banana" => "yellow"
    ),
    "vegetable" => array(
        "carrot" => "orange",
        "spinach" => "green"
    )
);

// Accessing apple's color from nested associative array
echo $nested_map["fruit"]["apple"]; // Output: red
?>

PHP

<?php
// Arrays within an array
$nested_array = array(
    array(1, 2, 3),
    array(4, 5, 6),
    array(7, 8, 9)
);

// Accessing the 3rd value from the 2nd array in nested indexed array
echo $nested_array[1][2]; // Output: 6
?>

PHP

<?php
// Arrays within an associative array
$map_of_arrays = array(
    "numbers" => array(1, 2, 3),
    "more_numbers" => array(4, 5, 6)
);

// Accessing the second value from the 'numbers' array in map_of_arrays
echo $map_of_arrays["numbers"][1]; // Output: 2
?>

PHP

<?php
// Associative array within an associative array
$nested_map = array(
    "fruit" => array(
        "apple" => "red", 
        "banana" => "yellow"
    ),
    "vegetable" => array(
        "carrot" => "orange",
        "spinach" => "green"
    )
);

// Modifying spinach's color to red
$nested_map["vegetable"]["spinach"] = "red";

// Adding cherry to the 'fruit' map in nested_map
$nested_map["fruit"]["cherry"] = "red";

// Deleting apple from the 'fruit' map in nested_map
unset($nested_map["fruit"]["apple"]);
?>

PHP

<?php
// Arrays within an array
$nested_array = array(
    array(1, 2, 3),
    array(4, 5, 6),
    array(7, 8, 9)
);

// Adding 10 to the first array in nested array
$nested_array[0][] = 10;

// Deleting the 2nd value from the 3rd array in nested array
unset($nested_array[2][1]);
?>