[Edit] PHP: Arrays

content/php/concepts/arrays/arrays.md

@@ -1,59 +1,289 @@
 ---
 Title: 'Arrays'
-Description: 'In PHP, an array is an ordered map that can hold more than one value.'
+Description: 'In PHP, an array is a special variable that can hold more than one value at a time.'
 Subjects:
-  - 'Web Development'
   - 'Computer Science'
+  - 'Web Development'
 Tags:
   - 'Arrays'
   - 'Data Types'
+  - 'Functions'
+  - 'Values'
 CatalogContent:
   - 'learn-php'
-  - 'paths/front-end-engineer-career-path'
   - 'paths/computer-science'
 ---
 
-An array can hold more than one value. In PHP, they're stored as value pairs that in other languages would be called a dictionary or a hashtable. Keys can be strings or integers.
+In PHP, an **array** is a special variable that can hold more than one value at a time. Rather than creating multiple variables to store related data, arrays group data logically under one variable name. PHP supports three main types of arrays:
+
+- **Indexed Arrays**: Arrays having a numeric index.
+- **Associative Arrays**: Arrays having named keys.
+- **Multidimensional Arrays**: Arrays having one or more arrays in it.
+
+## Creating Arrays
+
+There are different ways to create an array in PHP. Let's check them out one-by-one.
+
+### Indexed Arrays
+
+The `array()` function is used to create an indexed array:
+
+```php
+$colors = array("Red", "Green", "Blue");
+```
+
+Here is a shorter syntax that can also be used to create an indexed array:
+
+```php
+$colors = ["Red", "Green", "Blue"];
+```
+
+### Associative Arrays
+
+An associative array can be created like this:
+
+```php
+$person = [
+  "name" => "John",
+  "age" => 30,
+  "email" => "[email protected]"
+];
+```
+
+### Multidimensional Arrays
+
+A multidimensional array can be created like this:
+
+```php
+$users = [
+  ["name" => "Alice", "age" => 25],
+  ["name" => "Bob", "age" => 28]
+];
+```
+
+## Accessing Arrays
+
+There are different ways to access an array in PHP. Let's check them out one-by-one.
+
+### Indexed Arrays
+
+This example accesses the first item in the indexed array `colors`:
 
-## Syntax
+```php
+<?php
+$colors = ["Red", "Green", "Blue"];
+
+echo $colors[0]; // Output: Red
+?>
+```
+
+### Associative Arrays
+
+This example accesses the value associated with the `"name"` key in the associative array `person`:
+
+```php
+<?php
+$person = [
+  "name" => "John",
+  "age" => 30
+];
+
+echo $person["name"]; // Output: John
+?>
+```
+
+### Multidimensional Arrays
 
-There are several methods of declaring an array in PHP. The `array()` function can be used, either with key-value pairs, or with values alone. Single brackets, `[...]` can also be used in place of the `array()` keyword. If any key value is omitted, the key will be found by incrementing the largest prior integer key. If a key is repeated, the new value will overwrite the prior key.
+This example accesses the value associated with the `"name"` key for the second user in the multidimensional array `users`:
 
 ```php
 <?php
-// The last comma can be omitted
-$array1 = array( "item 1" => "one", "item 2" => "two", "item 3" => "three", );
+$users = [
+  ["name" => "Alice", "age" => 25],
+  ["name" => "Bob", "age" => 28]
+];
 
-echo $array1["item 1"], ";", $array1["item 2"], ";", $array1["item 3"];
-// Output: one;two;three
+echo $users[1]["name"]; // Output: Bob
+?>
+```
 
-$array2 = array("one", "two", "three");
+## Updating Arrays
 
-echo $array2[0], ";", $array2[1], ";", $array2[2];
-// Output: one;two;three
+This example updates the second item of the indexed array `colors` and the value associated with the key `"age"` in the associative array `person`:
 
-$array3 = ["one", 5 => "two", "three"];
+```php
+<?php
+$colors = ["Red", "Green", "Blue"];
 
-echo $array3[0], ";", $array3[5], ";", $array3[6];
-// Output: one;two;three
+$colors[1] = "Yellow";
 
-$array4 = [5 => "one", 5.7 => "two", "5" => "three"];
+$person = [
+  "name" => "John",
+  "age" => 30
+];
 
-echo $array4[5];
-// Output: three
+$person["age"] = 31;
+
+print_r($colors[1]);
+print_r("\n");
+print_r($person["age"]);
 ?>
 ```
 
-When defining an array, the following key casts will occur:
+Here is the output:
+
+```shell
+Yellow
+31
+```
+
+## Adding Items to an Array
+
+This example adds a new item to the indexed array `colors` and a new key-value pair to the associative array `person`:
 
-- Strings containing valid `int` types, unless preceded by a `+` sign, will be cast to an `int` type key.
-  As in the above example `"5"` is treated as `5`.
-- `float` types will be cast to `int` types, truncating the fractional part.
-  As in the above example `5.7` is treated as `5`.
-- `bool` types are cast to `int` types. `true` is stored as `1` and `false` stored as `0`.
-- `null` will be cast as the empty string, `""`.
-- Arrays and objects cannot be used as keys and will result in an error: `Illegal offset type`.
+```php
+<?php
+$colors = ["Red", "Green"];
 
-## Array Functions
+$colors[] = "Purple";
 
-Below is a list of selected array functions:
+$person = [
+  "name" => "John",
+  "age" => 30
+];
+
+$person["city"] = "New York";
+
+print_r($colors);
+print_r("\n");
+print_r($person);
+?>
+```
+
+Here is the output:
+
+```shell
+Array
+(
+  [0] => Red
+  [1] => Green
+  [2] => Purple
+)
+
+Array
+(
+  [name] => John
+  [age] => 30
+  [city] => New York
+)
+```
+
+## Removing Items from an Array
+
+This codebyte example uses the `unset()` function to remove an item from the indexed array `colors` and a key-value pair from the associative array `person`:
+
+```codebyte/php
+<?php
+$colors = ["Red", "Green", "Blue"];
+
+unset($colors[2]);
+
+$person = [
+  "name" => "John",
+  "email" => "[email protected]"
+];
+
+unset($person["email"]);
+
+print_r($colors);
+print_r("\n");
+print_r($person);
+?>
+```
+
+## Frequently Asked Questions
+
+### 1. How do I check if a value exists in an array?
+
+Using `in_array()` and `array_key_exists()`:
+
+```php
+<?php
+$colors = ["Red", "Green", "Blue"];
+$person = ["name" => "Alice", "age" => 25];
+
+if (in_array("Red", $colors)) {
+  echo "Red is in the array.\n";
+}
+
+if (array_key_exists("name", $person)) {
+  echo "The 'name' key exists.\n";
+}
+?>
+```
+
+Here is the output:
+
+```shell
+Red is in the array.
+The 'name' key exists.
+```
+
+### 2. How can I loop through an array in PHP?
+
+Using `foreach` to loop through indexed and associative arrays:
+
+```php
+<?php
+$colors = ["Red", "Green", "Blue"];
+
+foreach ($colors as $color) {
+  echo $color . "\n";
+}
+
+$person = ["name" => "Alice", "age" => 25];
+
+foreach ($person as $key => $value) {
+  echo "$key: $value\n";
+}
+?>
+```
+
+Here is the output:
+
+```shell
+Red
+Green
+Blue
+name: Alice
+age: 25
+```
+
+### 3. How do I count the number of elements in an array?
+
+You can use the built-in `count()` function to determine how many elements an array contains:
+
+```php
+<?php
+$colors = ["Red", "Green", "Blue"];
+
+echo "Total colors: " . count($colors);
+
+print_r("\n");
+
+$person = [
+  "name" => "John",
+  "age" => 30,
+  "email" => "[email protected]"
+];
+
+echo "Total fields: " . count($person);
+?>
+```
+
+Here is the output:
+
+```shell
+Total colors: 3
+Total fields: 3
+```