Error in printing data echo - PHP

I am printing a Urls with several data in a single echo the url to print is: http://localhost/prueba/profile.php and the values of the variables are: $ url = http:// $ host = localhost APP-RAIZ = prueba

Try the following form but print an error:

echo '<a href="'.$url $host APP_RAIZ.' profile.php">Iniciar Sesión</a>';

  

Parse error: syntax error, unexpected '$ host' (T_VARIABLE), expecting ',' or ';' in C: \ xampp \ htdocs \ test \ header.php on line 53

Try the following way but it also prints an error:

echo "<a href="'.$url $host APP_RAIZ.' profile.php">Iniciar Sesión</a>";

  

Parse error: syntax error, unexpected ''. $ url $ host; APP_RAIZ ;. '' (T_CONSTANT_ENCAPSED_STRING), expecting ',' or ';' in C: \ xampp \ htdocs \ test \ header.php on line 54

Of the following form also but without result.

echo '<a href=" '.$url.' '.$host.' '.APP_RAIZ;.' login.php">Iniciar Sesión</a>';

I have made another type of printing of several data in a single echo without any error, I do not see where I am doing wrong in printing the url

echo'<img src="img/upload/'.$pro['image'].'" alt="'.$pro['profile'].'" />';