The json_encode() function in PHP is a built-in function that converts PHP values into JSON format. JSON, or JavaScript Object Notation, is a lightweight data-interchange format that is easy for humans to read and write and easy for machines to parse and generate.

The json_encode() function takes a single argument, which is the value to be encoded. The value can be any PHP type, including arrays, objects, strings, integers, floats, and booleans. The function returns a string containing the JSON representation of the value.

 
 
// Define an array of ships
$ships = array(
    array("name" => "Titanic", "type" => "passenger", "sunk" => true),
    array("name" => "Bismarck", "type" => "battleship", "sunk" => true),
    array("name" => "Enterprise", "type" => "aircraft carrier", "sunk" => false)
);
 
// Encode the array as a JSON string
$json = json_encode($ships);
 
// Print the JSON string
echo $json;
 
Output:
[{"name":"Titanic","type":"passenger","sunk":true},{"name":"Bismarck","type":"battleship","sunk":true},{"name":"Enterprise","type":"aircraft carrier","sunk":false}]
 
 

This example shows how the php json_encode function converts an array of associative arrays into a JSON array of objects. Each object has three properties: name, type, and sunk. The boolean values are encoded as true or false in JSON.

Encoding an Object:

This example encodes an object of the Ship class into JSON format. 

 
 
 
class Ship {
    public $name;
    public $capacity;
 
    public function __construct($name, $capacity) {
        $this->name = $name;
        $this->capacity = $capacity;
    }
}
 
$ship = new Ship("Queen Mary", 2000);
$json = json_encode($ship);
echo $json;
 
Output: 
 
{"name":"Queen Mary","capacity":2000}
 

Array to JSON array 

 
$students = array(
    array('name' => 'John', 'age' => 20, 'grade' => 'A'),
    array('name' => 'Alice', 'age' => 22, 'grade' => 'B')
);
 
$json_students = json_encode($students);
 
echo $json_students;
 
Output:
[{"name":"John","age":20,"grade":"A"},{"name":"Alice","age":22,"grade":"B"}]
 

Here, we have an array of student records. json_encode will convert it into a JSON array.

Array to JSON string

 
$ship = [
    "name" => "Evergreen",
    "type" => "Container ship",
    "capacity" => 20000,
    "builtYear" => 2019
];
 
$jsonString = json_encode($ship);
echo $jsonString;
 
This code will output the following JSON string: 
 
{"name":"Evergreen","type":"Container ship","capacity":20000,"builtYear":2019}