<form>
    Username:<br>
    <input type="text" name="username"><br>
    Password:<br>
    <input type="text" name="password">
    <input type="button" value="submit" ng-click="testDatabaseNewUser()">
</form>

angular.module('appDatabaseCtrl', [])
.controller('databaseCtrl', ['$scope', '$http', '$log',
    function($scope, $http, $log){
        $scope.testDatabaseNewUser = function(){
            $http.post('api/New_User').success(function(data) {
                $log.info("succes!");
                $log.log(data);
            })
            .error(function (data, status){
                $log.error("error!");
                $log.log(data);
            });
        };
    }
]);

<?php

require 'vendor/autoload.php';
require 'config/config.php';

$app = new SlimApp;

$app->post('/New_User', 'addUser');

$app->run();

function DB_Connection() {
    global $dbparams;
    $dbhost = $dbparams['host'];
    $dbuser = $dbparams['user'];
    $dbpass = $dbparams['password'];
    $dbname = $dbparams['dbname'];
    $dbh = new PDO("mysql:host=$dbhost;dbname=$dbname", $dbuser, $dbpass);
    $dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    return $dbh;
}

function addUser($req, $resp, $args) {
    ...
}

?>