techmore.in

PHP - Arrays

Arrays in PHP are versatile and allow you to store multiple values in a single variable. They are essential for handling collections of data, such as lists of items, sets of key-value pairs, and more complex data structures. Here's a comprehensive overview of how arrays work in PHP:

1. Indexed Arrays

Indexed arrays are arrays where each element is assigned a numeric index starting from 0.

Creating Indexed Arrays

You can create indexed arrays using the array() construct or using square brackets [] since PHP 5.4.

Example:

php
<?php
        // Using array() construct
        $colors = array("Red", "Green", "Blue");
        
        // Using square brackets []
        $numbers = [1, 2, 3, 4, 5];
        ?>

Accessing Elements

You can access elements of an indexed array using their numeric index.

Example:

php
<?php
        echo $colors[0]; // Outputs: Red
        echo $numbers[2]; // Outputs: 3
        ?>

Modifying Elements

You can modify elements of an indexed array by assigning a new value to a specific index.

Example:

php
<?php
        $colors[1] = "Yellow";
        print_r($colors); // Outputs: Array ( [0] => Red [1] => Yellow [2] => Blue )
        ?>

2. Associative Arrays

Associative arrays are arrays where each element is associated with a specific key instead of a numeric index.

Creating Associative Arrays

You can create associative arrays using the array() construct or using square brackets [].

Example:

php
<?php
        // Using array() construct
        $person = array(
            "name" => "John",
            "age" => 30,
            "city" => "New York"
        );
        
        // Using square brackets []
        $book = [
            "title" => "PHP Handbook",
            "author" => "John Doe",
            "year" => 2023
        ];
        ?>

Accessing Elements

You can access elements of an associative array using their keys.

Example:

php
<?php
        echo $person["name"]; // Outputs: John
        echo $book["author"]; // Outputs: John Doe
        ?>

Modifying Elements

You can modify elements of an associative array by assigning a new value to a specific key.

Example:

php
<?php
        $person["age"] = 35;
        print_r($person); // Outputs: Array ( [name] => John [age] => 35 [city] => New York )
        ?>

3. Multidimensional Arrays

Multidimensional arrays are arrays that contain other arrays as elements. They can be indexed or associative.

Creating Multidimensional Arrays

Example of Indexed Multidimensional Array:

php
<?php
        $matrix = array(
            array(1, 2, 3),
            array(4, 5, 6),
            array(7, 8, 9)
        );
        ?>

Example of Associative Multidimensional Array:

php
<?php
        $users = array(
            "user1" => array(
                "name" => "John",
                "age" => 30
            ),
            "user2" => array(
                "name" => "Jane",
                "age" => 25
            )
        );
        ?>

Accessing Elements in Multidimensional Arrays

You can access elements in multidimensional arrays using multiple indices.

Example:

php
<?php
        echo $matrix[1][2]; // Outputs: 6
        echo $users["user1"]["name"]; // Outputs: John
        ?>

4. Array Functions

PHP provides a variety of built-in functions to manipulate arrays, such as:

  • count(): Returns the number of elements in an array.
  • array_push(): Adds one or more elements to the end of an array.
  • array_pop(): Removes and returns the last element of an array.
  • array_merge(): Merges one or more arrays into a single array.
  • array_key_exists(): Checks if a specified key exists in an array.

Example:

php
<?php
        $numbers = [1, 2, 3, 4, 5];
        echo count($numbers); // Outputs: 5
        
        array_push($numbers, 6);
        print_r($numbers); // Outputs: Array ( [0] => 1 [1] => 2 [2] => 3 [3] => 4 [4] => 5 [5] => 6 )
        
        $last = array_pop($numbers);
        echo $last; // Outputs: 6
        
        $newArray = array_merge($colors, $numbers);
        print_r($newArray); // Outputs: Array ( [0] => Red [1] => Green [2] => Blue [3] => 1 [4] => 2 [5] => 3 [6] => 4 [7] => 5 )
        
        if (array_key_exists("name", $person)) {
            echo "Name exists in person array.";
        }
        ?>