phpMyAdmin добавление стоки в таблицу

Я новичек в PHP и хотел задать вопрос по поводу работы с БД. Я пытаюсь реализовать систему регистрации, но после заполнения формы регистрации строка в таблицу "users" в базе данных не добавляется. Как это можно исправить?

functions.php:

<?php
include 'C:\OpenServer\domains\localhost\mtalk_includes\config.php';

function getDatabaseConnection() {
    try {
        $conn = new PDO( 'mysql:host=' . DB_HOST . ';dbname=' . DB_NAME, DB_USER, DB_PASS);
        return $conn;
    } catch ( PDOException $e ) {
        return $e->getMessage();
    }
}

function getUserWithEmailAddress( $email ) {
    $databaseConnection = getDatabaseConnection();
    
    $statement = $databaseConnection->prepare( '
        SELECT
            *
        FROM
            users
        WHERE
            email = :email
    ' );

    $statement->setFetchMode( PDO::FETCH_ASSOC );
    $statement->execute( array(
        'email' => trim( $email )
    ) );

    $user = $statement->fetch();
    return $user;
}

function signUserUp ( $info ) {
    $databaseConnection = getDatabaseConnection();

    $statement = $databaseConnection->prepare( '
        INSERT INTO 
            users (
                email,
                first_name,
                last_name,
                password,
                key_value
            )
        VALUES (
                :email,
                :first_name,
                :last_name,
                :password,
                :key_value
        )
    ' );
    
    $statement->execute( array(
        'email' => trim( $info['email'] ),
        'first_name' => trim( $info['first_name'] ),
        'last_name' => trim( $info['last_name'] ),
        'password' => hashedPassword( $info['password'] ),
        'key_value' => newKey(),
    ) );

    return $databaseConnection->lastInsertId();


}

function newKey( $length = 32 ) {
    $time = md5( uniqid() ) . microtime();
    return substr( md5( $time ), 0, $length );
}

function hashedPassword( $password ) {
    $random = openssl_random_pseudo_bytes( 18 );
    $salt = sprintf( '$2y$%02d$%s',
        12,
        substr( strtr( base64_encode( $random ), '+', '.' ), 0, 22 )
    );

    
    $hash = crypt( $password, $salt );

    return $hash;
}

config.php:

<?php
define( 'DB_HOST', 'localhost' );
define( 'DB_NAME', 'test' );
define( 'DB_USER', 'root'); 
define( 'DB_PASS', '');

process_signup.php:

<?php
include 'functions.php';

$userInfo = getUserWithEmailAddress( trim( $_POST['email'] ) );

$status = 'ok';
$message = 'valid';

$userId = signUserUp( $_POST );

echo json_encode(
    array(
        'status' => $status,
        'message' => $message
    )
);

signup.php:

<script type="text/javascript" src="js/loader.js"></script>
<script type="text/javascript" src="js/jquery.js"></script>

        <script>
        $( function() {

            $( '#signup_button' ).on( 'click', function() {
                processSignup();
            } );

            $( '.form-input' ).keyup( function( e ) {
                if ( e.keyCode == 13 ) {
                    processSignup();
                }
            } );
        } );

        function processSignup() {
            $( '#error_message' ).html( '' );
            $( 'input' ).removeClass( 'invalid-input' );

            var allFieldsFilledIn = true;

            $( 'input' ).each( function() {
                if ( '' == $( this ).val() ) {
                    $( this ).addClass( 'invalid-input ');
                    allFieldsFilledIn = false;
                }
            } );

            if ( allFieldsFilledIn ) {

                $.ajax( {
                    url: 'php/process_signup.php',
                    data: $( '#signup_form' ).serialize(),
                    type: 'post',
                    dataType: 'json',
                    success: function( data ) {
                        if ( 'ok' == data.status ) {
                            loader.hideLoader();
                            window.location.href = "login.php";
                        } else if ( 'fail' == data.status ) {
                            $( '#error_message' ).html( data.message );
                        }
                    }
                } );
            } else {
                $( '#error_message' ).html( 'All fields must be filled in.' );
                $( window ).scrollTop( 0 );
            }
        }
    </script>