php数组怎么转成json字符串

<?php$fruits = array("apple", "banana", "orange");echo json_encode($fruits);?>

["apple","banana","orange"]

<?php$person = array("name" => "John", "age" => 30, "city" => "New York");echo json_encode($person);?>

{"name":"John","age":30,"city":"New York"}

<?php$people = array(    array("name" => "John", "age" => 30),    array("name" => "Jane", "age" => 25));echo json_encode($people);?>

[{"name":"John","age":30},{"name":"Jane","age":25}]

{    "name": "John",    "age": 30,    "city": "New York",    "fruits": ["apple", "banana", "orange"]}

<?php$json_string = '{    "name": "John",    "age": 30,    "city": "New York",    "fruits": ["apple", "banana", "orange"]}';$obj = json_decode($json_string);$fruits = $obj->fruits;print_r($fruits);?>

Array ( [0] => apple [1] => banana [2] => orange )