How to convert an array to JSON

Short answer

json_encode() turns an array into a JSON string:

<?php
 
echo json_encode(['name' => 'Anna', 'age' => 25]);

Output:

{"name":"Anna","age":25}

Non-ASCII letters and a readable layout

The flags are joined with a vertical bar:

<?php
 
echo json_encode(['city' => 'Zürich'], JSON_UNESCAPED_UNICODE | JSON_PRETTY_PRINT);

Output:

{
    "city": "Zürich"
}

A list or an object

An array with keys numbered from zero becomes a list, any other becomes an object:

<?php
 
echo json_encode(['a', 'b']), ' ', json_encode([1 => 'a', 2 => 'b']);

Output:

["a","b"] {"1":"a","2":"b"}