There is no such tag as "{{}}".
But it can be done something like this example:
<?
$companyName = "Name";
$companyLogo = "Logo Url";
$html = "...{{companyName}} and {{companyLogo}}...";
$tags = array('{{companyName}}' , '{{companyLogo}}');
$values = array($companyName, $companyLogo);
$replaced = str_replace($tags,$values,$html);
echo $replaced;
?>