Web Technologies Tutorial

Introduction to PHP Arrays

Arrays in PHP are versatile data structures that can store multiple values in a single variable. They are essential for organizing and manipulating data in PHP applications. PHP offers several types of arrays and numerous built-in functions for array manipulation.

Creating Arrays

There are multiple ways to create arrays in PHP:


<?php
// Using array() function
$fruits = array("Apple", "Banana", "Orange");

// Using square bracket syntax (PHP 5.4+)
$colors = ["Red", "Green", "Blue"];

// Creating an empty array
$emptyArray = [];
?>

Indexed Arrays

Indexed arrays use numeric keys, starting from 0 by default.


<?php
$cars = ["Volvo", "BMW", "Toyota"];
echo $cars[0]; // Outputs: Volvo

// Adding a new element
$cars[] = "Honda";
?>

Associative Arrays

Associative arrays use named keys that you assign to them.


<?php
$age = ["Peter" => 35, "Ben" => 37, "Joe" => 43];
echo $age["Ben"]; // Outputs: 37

// Adding a new element
$age["Mary"] = 29;
?>

Multidimensional Arrays

Multidimensional arrays contain one or more arrays as their elements.


<?php
$employees = [
    ["John", "Doe", "john@example.com"],
    ["Mary", "Smith", "mary@example.com"]
];
echo $employees[1][0]; // Outputs: Mary

$users = [
    "John" => ["age" => 30, "city" => "New York"],
    "Mary" => ["age" => 25, "city" => "London"]
];
echo $users["Mary"]["city"]; // Outputs: London
?>

Array Functions

PHP provides numerous built-in functions for working with arrays:


<?php
$numbers = [3, 1, 4, 1, 5, 9];

// Count elements
echo count($numbers); // Outputs: 6

// Sort array
sort($numbers);
print_r($numbers); // Outputs: Array ( [0] => 1 [1] => 1 [2] => 3 [3] => 4 [4] => 5 [5] => 9 )

// Reverse array
$reversed = array_reverse($numbers);
print_r($reversed); // Outputs: Array ( [0] => 9 [1] => 5 [2] => 4 [3] => 3 [4] => 1 [5] => 1 )

// Check if element exists
if (in_array(5, $numbers)) {
    echo "Found 5";
}

// Get array keys
$fruits = ["a" => "apple", "b" => "banana"];
print_r(array_keys($fruits)); // Outputs: Array ( [0] => a [1] => b )

// Merge arrays
$array1 = [1, 2, 3];
$array2 = [4, 5, 6];
$merged = array_merge($array1, $array2);
print_r($merged); // Outputs: Array ( [0] => 1 [1] => 2 [2] => 3 [3] => 4 [4] => 5 [5] => 6 )
?>

Array Iteration

PHP offers several ways to iterate through arrays:


<?php
$colors = ["red", "green", "blue"];

// Using for loop
for ($i = 0; $i < count($colors); $i++) {
    echo $colors[$i] . " ";
}

// Using foreach loop
foreach ($colors as $color) {
    echo $color . " ";
}

// Using foreach with key => value
$age = ["Peter" => 35, "Ben" => 37, "Joe" => 43];
foreach ($age as $name => $value) {
    echo "$name is $value years old. ";
}
?>

Array Unpacking (PHP 7.4+)

PHP 7.4 introduced the spread operator for arrays, allowing easy unpacking of arrays.


<?php
$fruit = ["apple", "orange"];
$vegetables = ["carrot", "pea"];
$food = [...$fruit, ...$vegetables];
print_r($food); // Outputs: Array ( [0] => apple [1] => orange [2] => carrot [3] => pea )
?>

Array Destructuring

PHP allows you to unpack arrays into distinct variables.


<?php
$info = ["John Doe", "john@example.com", 35];
[$name, $email, $age] = $info;
echo "Name: $name, Email: $email, Age: $age";
// Outputs: Name: John Doe, Email: john@example.com, Age: 35
?>

Best Practices

Use meaningful names for array keys in associative arrays.
Prefer foreach loops for iterating over arrays when the key is not needed.
Use array functions like array_map(), array_filter(), and array_reduce() for functional programming style operations.
Be cautious with large arrays to avoid memory issues.
Use type hinting (array) for function parameters and return types when working with arrays.
Consider using array unpacking for merging arrays instead of array_merge() for better performance with a large number of arrays.

Conclusion

Arrays are fundamental data structures in PHP, offering powerful ways to store and manipulate collections of data. Understanding how to create, modify, and iterate through arrays is crucial for effective PHP programming. As you continue to work with PHP, you'll find arrays to be indispensable in handling complex data structures and implementing various algorithms.

PHP: Arrays