<?php
function tag($tag, $content = null, array $attributes = null) {

   $out = '<{$tag}';
   if ($attributes !== null) {
     foreach($attributes AS $key => $val) {
       $out .= ' {$key}="{$val}"';
     }
   }

   if ($content === null) {
      return '{$out}/>';
   }

   return '{$out}>{$content}</{$tag}>';

}

tag('h1', 'Header', array('class' => 'h1', 'id' => 'h1', 'style' => 'text-align:center;'));