<?php

function miniTemplate($text, $data) { 
    return preg_replace_callback('~\{\{(.*?)}}~', function ($m) use ($data) {
                 return isset($data[$m[1]]) ? $data[$m[1]] : $m[0]; 
           }, $text);
}
$text = "Hello {{var1}}, nice to meet {{var2}} at {{var3}}";
$data = array("var1" => "World", "var2"=> "You");
echo miniTemplate($text, $data);