SQLSTATE[HY000] [1045] Access denied for user 'username_a'@'localhost'

Question

I'm trying to get MariaDb to

a) create a database

b) create a user for the database

c) create a table for the database

d) insert data into the new table

However, the code doesn't

a) create a table

b) log in as the new user and insert the data into the table

The PHP code:

$MariaDb_User_Username = "username_a";
$MariaDb_User_Password = "password_a";
$MariaDb_User_Database = "database_a";

$Admin_Username = "Admin";
$Admin_Password = "asd123";

try{
    $Dbh1 = new PDO("mysql:host=127.0.0.1:3307", $Admin_Username, $Admin_Password);
    $Dbh1->exec("CREATE DATABASE `{$MariaDb_User_Database}`;");         //'
    echo "A complete<br>";
}
catch (PDOException $e) 
{
    echo 'A Error:'.$e->getCode().':<br>'.$e->getMessage().'<br>'; //die($e->getMessage()); //'.$e->errorInfo().'<br>
}

try{
    $Dbh2 = new PDO("mysql:host=127.0.0.1:3307", $Admin_Username, $Admin_Password);
    $Dbh2->exec("CREATE USER IF NOT EXISTS `{$MariaDb_User_Username}`@`127.0.0.1:3307` IDENTIFIED BY `{$MariaDb_User_Password}`;
            GRANT SELECT, INSERT, UPDATE, DELETE ON `{$MariaDb_User_Database}`.* TO `{$MariaDb_User_Username}`@`127.0.0.1:3307`; 
            FLUSH PRIVILEGES;");
    echo "B complete<br>";
}
catch (PDOException $e) 
{
    echo 'B Error:'.$e->getCode().':<br>'.$e->getMessage().'<br>'; //die($e->getMessage()); //'.$e->errorInfo().'<br>
}

try{
    $Dbh3 = new PDO("mysql:host=127.0.0.1:3307", $Admin_Username, $Admin_Password);
    $Dbh3->exec("CREATE TABLE Tablename(
     rowid INT( 255 ) AUTO_INCREMENT PRIMARY KEY,
     fname VARCHAR( 255 ) NOT NULL, 
     sname VARCHAR( 255 ) NOT NULL,
     age INT( 3 )");
     echo "C complete<br>";
}
catch (PDOException $e) 
{
    echo 'C Error:'.$e->getCode().':<br>'.$e->getMessage().'<br>'; //die($e->getMessage()); //'.$e->errorInfo().'<br>
}

try{
    $Dbh4 = new PDO("mysql:host=127.0.0.1:3307;dbname=$MariaDb_User_Database", $MariaDb_User_Username, $MariaDb_User_Password); 
    $statement = $Dbh4->prepare('INSERT INTO '.$MariaDb_User_Database.' (name, lastname, age)
        VALUES (:fname, :sname, :age)');

    $statement->execute([
        'fname' => 'Bob',
        'sname' => 'Desaunois',
        'age' => '18',
]);     
    echo "D complete<br>";
}
catch (PDOException $e) 
{
    echo 'D Error:'.$e->getCode().':<br>'.$e->getMessage().'<br>'; //die($e->getMessage()); //'.$e->errorInfo().'<br>
}

Also, the user is created when checking in PhpMyAdmin->MariaDb, it shows the following credentials:

USERNAME: username_a

HOSTNAME: 127.0.0.1:3307

TYPE: wildcard:database_a

PRIVILEGES: SELECT,INSERT,UPDATE,DELETE

GRANT: No

The only response I'm getting is:

A complete
B complete
C complete
D Error:1045:
SQLSTATE[HY000] [1045] Access denied for user 'username_a'@'localhost' (using password: YES)

which is weird because C was never completed as well as D.

Thanks.