如何在onclick上多次使用PHP echo

Question

I'm trying to add some php into onclick button

This works fine:

<a onclick="welcomeDiv(welcomeDiv6);"></a>

However if I try this:

echo '<a onclick="welcomeDiv(welcomeDiv'.$cols.');"></a>';

It doesn't work, error: TypeError: div is null. It's weird because the $cols works.

Also for multiple elements:

echo '<a onclick="
  document.getElementById("iframeHolder'.$cols.'").src=
  "'.JRoute::_(SEO::getItemRoute($i->id.':'.$i->alias,$i->cat_id.':'
    .$i->c_alias))
    .';welcomeDiv("welcomeDiv'.$cols.'");""
  ></a>';