Passing json array from angularJS to PHP to json file -> malformed json

at start, I come with a JSON array, like this one :

[
    {
        "login":"Admin",
        "admin":true,
        "root":true
    },
    {
        "login":"PMO",
        "admin":true,
        "root":false
    }
]

I want to overwrite the content of this JSON array by another, which is into the variable $scope.users I first send it to a PHP file from a controller :

$http.post('php/users/deleteUser.php', $scope.users);

which overwrites the old json file

<?php
    $data = file_get_contents("php://input");
    file_put_contents('../users/users.json', $data);
?>

But when I open the file users.json, the content is malformed :

0%5Blogin%5D=Admin&0%5Badmin%5D=true&0%5Broot%5D=true&0%5B%24%24hashKey%5D=01R&1%5Blogin%5D=PMO.....

I don't manage to get where it comes from. I've tried all possible combinations with JSON.parse, JSON.stringify, json_encode, json_decode. I also tried to write the $http request like this :

$http({
    method:"POST",
    url:'php/users/deleteUser.php',
    data:$scope.users,
    headers: {'Content-Type': 'application/json'}
});

But nothing changes the result. Any idea ?