styles from php script?

I would like to apply styles using html elements created with php, try giving it an id but it has a not very correct function as for example I can not modify the width or height

function loginbutton($buttonstyle = "square") {
    $button['rectangle'] = "01";
    $button['square'] = "02";
    $button = "<a  href='?login' id='buttonin'><i  class='fab fa-steam-symbol logando'></i><p id='st'>Steam Log</p></a>";

    echo $button;
}

and in the styles it does not work if I give text decoration none to #buttonin, any help? : (