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Arrays in PHP

Arrays are a strong data-handling tool in PHP. Arrays are a type of data structure that enables programmers to store and manipulate several values in a single variable. They are incredibly adaptable and may be utilized in a wide range of applications, from basic lists to complicated data structures. We will cover all you need to know to master dealing with PHP arrays in this comprehensive guide.

Understanding the Basics of PHP Arrays

There are two main types of arrays in PHP: indexed and associative.

Indexed Arrays

Indexed arrays are made by assigning many values to a single variable, each with its own integer index. As an example:

$fruits = array("apple", "banana", "orange"); 

In this example, “apple” has the index 0, “banana” has the index 1, and “orange” has the index 2. These values may be accessed by using the array’s index, as seen below:

echo $fruits[0]; // outputs "apple"

Associative Arrays

In contrast, associative arrays are built by assigning keys (strings or numbers) to values. As an example:

$person = array("name" => "John Smith", "age" => 30, "address" => "123 Main St.");

In this example, “name” is set to “John Smith,” “age” is set to “30,” and “address” is set to “123 Main St.”. These values may be accessed by using the array’s keys as follows:

echo $person["name"]; // outputs "John Smith"

Creating Arrays

There are several ways to create arrays in PHP, including:

• Using the array() function
• Using the square brackets []
• Using the range() function

Using the array() Function

In PHP, the array() method is the most often used technique to generate an array. As an example:

$fruits = array("apple", "banana", "orange");

Using Square Brackets

You can also create an array using square brackets [] in PHP 5.4 and later versions. For example:

Using the range() Function

The range() function creates an array of numbers within a specified range. For example:

This creates an array of numbers from 1 to 10.

Accessing Array Elements

You can access the elements of an array using the index or key of the element. For example:

$fruits = array("apple", "banana", "orange"); echo $fruits[0]; // outputs "apple"

$person = array("name" => "John Smith", "age" => 30, "address" => "123 Main St."); echo $person["name"]; // outputs "John Smith"

Modifying Array Elements

You can modify the elements of an array by assigning a new value to the index or key of the element. For example:

$fruits = array("apple", "banana", "orange"); $fruits[0] = "mango";

In this example, the value at index 0 of the $fruits array is changed from “apple” to “mango”.

Similarly, for associative arrays:

$person = array("name" => "John Smith", "age" => 30, "address" => "123 Main St."); $person["name"] = "Jane Doe";

The value of the key “name” in the $person array is changed from “John Smith” to “Jane Doe” in this example.

Advanced Array Manipulation

After you’ve mastered the fundamentals of arrays, you may go on to more complex array manipulation techniques.

Sorting Arrays

PHP has a number of built-in functions for sorting arrays, including sort(), usort(), and ksort (). Each of these methods organizes the items of an array in a different way, and you may select the one that best meets your requirements.

This will sort the elements of the $fruits array in ascending alphabetical order.

Merging and Splicing Arrays

You can merge two or more arrays together using the array_merge() function, like so:

$fruits1 = array("apple", "banana"); $fruits2 = array("orange", "grapes"); $fruits = array_merge($fruits1, $fruits2); 

This will generate a new array containing all of the entries from $fruits1 and $fruits2. You may also use the array splice() method to delete entries from an array, as seen below:

This will remove the element at index 1 from the $fruits array.

Iterating Through Arrays

You can iterate through the elements of an array using a for loop or a foreach loop, like so:

Filtering Arrays

You can filter the elements of an array using the array_filter() function, like so:

$filtered = array_filter($fruits, function ($fruit) < return $fruit != 'banana'; >);

This will create a new array that contains all elements of $fruits except for ‘banana’.

Working with Nested Arrays

Nested arrays are arrays that include one or more other arrays. They may be used to store sophisticated data structures.

Creating Nested Arrays

You can create a nested array by including an array as an element of another array. For example:

$fruits = array("apple", "banana", array("orange", "grapes"));

This creates an array $fruits with 3 elements

, where the third element is an array containing “orange” and “grapes”.

Accessing Elements in Nested Arrays

To access an element in a nested array, you must supply the element’s index or key at each level of the nested array. As an example:

$fruits = array("apple", "banana", array("orange", "grapes")); echo $fruits[2][0]; // outputs "orange"

Modifying Elements in Nested Arrays

You can modify an element in a nested array by specifying the index or key of the element in each level of the nested array. For example:

$fruits = array("apple", "banana", array("orange", "grapes")); $fruits[2][0] = "mango";

The value at index 0 of the third element (an array) of the $fruits array is changed from “orange” to “mango” in this example.

Iterating Through Nested Arrays

You can iterate through the elements of a nested array using nested loops. For example:

foreach ($fruits as $fruit) < if (is_array($fruit)) < foreach ($fruit as $subFruit) < echo $subFruit; >> else < echo $fruit; >>

This will output all elements of the nested array $fruits.

Built-in PHP Array Functions

PHP has a number of built-in functions for working with arrays. The following are some of the most regularly utilized functions:

• count() : returns the number of elements in an array
• sort() : sorts the elements of an array
• implode() : converts an array into a string
• explode() : converts a string into an array
• array_keys() : returns all the keys of an array
• array_values() : returns all the values of an array
• array_unique() : removes duplicate values from an array

Best Practices for Working with PHP Arrays

• Choosing the right data type: It is important to choose the right data type for your array, as it can have a big impact on performance and memory usage.
• Optimizing performance: Avoid using large arrays or performing complex operations on them, as they can cause performance issues.
• Error handling and debugging: Always check for errors and debug your code when working with arrays.
• Security considerations: Be aware of potential security issues when working with arrays, such as SQL injection and cross-site scripting.

Real-world Examples of Using Arrays

• Data storage and retrieval from a database: Arrays are frequently used to store data retrieved from a database and then used to display it on a webpage.
• Developing a basic to-do list app: In a to-do list application, arrays may be used to store and manage a list of tasks.
• Creating a contact form: Arrays may be used to store and validate data sent via a contact form.
• Creating a simple shopping cart: Arrays can be used to store and manage the items in a shopping cart.

Q&A

Q: What are the two main types of arrays in PHP?
A: The two main types of arrays in PHP are indexed arrays and associative arrays.

Q: How do you create an indexed array in PHP?
A: To create an indexed array in PHP, you can use the array() function or square brackets [] in PHP 5.4 and later versions. For example: $fruits = array(«apple», «banana», «orange»);

Q: How do you access an element in an indexed array?
A: To access an element in an indexed array, you can use the element’s index. For example: $fruits = array(«apple», «banana», «orange»); echo $fruits[0]; // outputs «apple»

Q: How do you create an associative array in PHP?
A: To create an associative array in PHP, you can use the array() function and assign keys to values. For example: $person = array(«name» => «John Smith», «age» => 30, «address» => «123 Main St.»);

Q: How do you access an element in an associative array?
A: To access an element in an associative array, you can use the element’s key. For example: $person = array(«name» => «John Smith», «age» => 30, «address» => «123 Main St.»); echo $person[«name»]; // outputs «John Smith»

Q: What is a nested array?
A: A nested array is an array that contains one or more arrays inside it. They are useful for storing complex data structures.

Q: How do you iterate through a nested array?
A: To iterate through a nested array, you can use nested loops. For example: foreach ($fruits as $fruit) < if (is_array($fruit)) < foreach ($fruit as $subFruit) < echo $subFruit; >> else < echo $fruit; >>

Q: What is the function to sort an array in PHP?
A: The built-in function to sort an array in PHP is sort() . For example: sort($fruits);

Q: What is the function to remove duplicates from an array in PHP?
A: The built-in function to remove duplicates from an array in PHP is array_unique() . For example: $unique = array_unique($fruits);

Q: What are some best practices to keep in mind when working with PHP arrays?
A: When dealing with PHP arrays, some best practices include selecting the appropriate data type, maximizing efficiency, managing errors and debugging, and being mindful of any security risks.

Exercises

1. Create an array containing the numbers 1 through 10.
2. Create a script to output the third member of an array.
3. Create a script that appends 5 to the end of an array.
4. Create a script that searches an array for the greatest value and puts it in a variable.
5. Create a script that sorts an array descendingly.

Answers:

1. $numbers = range(1,10);
2. echo $array[2];
3. $array[] = 5;
4. $highest = max($array);
5. rsort($array);

Источник

Как вывести PHP массив

Примеры использования PHP функций и циклов для вывода всех элементов массива в окно браузера.

Функция print_r()

Функция print_r() выводит информацию о переменной в удобочитаемом виде. Чтобы отобразить пробелы и переносы результат функции нужно обернуть в тег .

$array = array( 'Andi', 'Benny', 'Cara', 'Danny', 'Emily', ); echo '
'; print_r($array); echo '
 
'; 
 
Результат:
 
Array ( [0] => Andi [1] => Benny [2] => Cara [3] => Danny [4] => Emily )
 
 Функция var_dump() 
 
Функция var_dump() отображает информацию о переменной, включая тип и значение.
 
$array = array( 'Andi', 'Benny', 'Cara', 'Danny', 'Emily', ); echo '
'; var_dump($array); echo '
 
'; 
 
Результат:
 
array(5) < [0]=>string(4) "Andi" [1]=> string(5) "Benny" [2]=> string(4) "Cara" [3]=> string(5) "Danny" [4]=> string(5) "Emily" >
 
 var_export() 
 
Функция var_export() возвращает строковое представление переменной в виде полноценного PHP-кода.
 
$array = array( 'Andi', 'Benny', 'Cara', 'Danny', 'Emily', ); echo '
'; echo var_export($array); echo '
 
';
 
Результат:
 
array ( 0 => 'Andi', 1 => 'Benny', 2 => 'Cara', 3 => 'Danny', 4 => 'Emily', )
 
 Цикл foreach 
 
Цикл foreach специально создан для поэлементного перебора массивов.
 
$array = array( 'Andi', 'Benny', 'Cara', 'Danny', 'Emily', ); foreach ($array as $row) < echo $row . "
\r\n"; >
 
Результат:
 
Andi 
Benny 
Cara 
Danny 
Emily
 
Пример с выводом нумерованного списка с использованием индексов массива:
 
$array = array( 'Andi', 'Benny', 'Cara', 'Danny', 'Emily', ); foreach ($array as $n => $row) < echo ($n + 1) . '.' . $row . "
\r\n"; >
 
Результат:
 
1.Andi 
2.Benny 
3.Cara 
4.Danny 
5.Emily
 
Чтобы не выводить последний 
, добавим условие:
 
$array = array( 'Andi', 'Benny', 'Cara', 'Danny', 'Emily', ); foreach ($array as $n => $row) < echo ($n + 1) . '.' . $row; if ($n < count($array) - 1) < echo "
\r\n"; > >
 
Результат:
 
1.Andi 
2.Benny 
3.Cara 
4.Danny 
5.Emily
 
 Цикл for 
 
Цикл for подойдет только в случаях, когда индексы массива имеют непрерывную нумерацию.
 
$array = array( 'Andi', 'Benny', 'Cara', 'Danny', 'Emily', ); for ($n = 0; $n < count($array); $n++) < echo $n + 1 . '.' . $array[$n] . "
\r\n"; >
 
Результат:
 
1.Andi 
2.Benny 
3.Cara 
4.Danny 
5.Emily
 
 Цикл while 
 
Цикл while такое же работает как и for .
 
$array = array( 'Andi', 'Benny', 'Cara', 'Danny', 'Emily', ); $index = 0; while ($index < count($array)) < echo $index + 1 . '.' . $array[$index] . "
\r\n"; $index++; >
 
Результат:
 
1.Andi 
2.Benny 
3.Cara 
4.Danny 
5.Emily
 
 Функция implode() 
 
Также, для вывода массива удобно использовать функцию implode() , которая объединяет элементы массива через разделитель.
 
$array = array( 'Andi', 'Benny', 'Cara', 'Danny', 'Emily', ); echo implode("
\r\n", $array);
 
Результат:
 
Andi 
Benny 
Cara 
Danny 
Emily
 
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