<?php
    $delimited = 'Hello %%NAME%%, your %%CAR%% is ready to pickup from %%STORE%%';
    $delim = '%%';
    $matches = array();
    $pattern = '~'.$delim.'(.*?)'.$delim.'~';

    echo($pattern.PHP_EOL);

    $filter = new MyFilter();
    die(preg_replace_callback($pattern,array($filter,'findFilter'),$delimited));

    class MyFilter
    {   
        private $filter;

        public function MyFilter()
        {   
            $this->filter = array('NAME'  => 'Iain Dooley',
                                  'CAR'   => 'Honda',
                                  'STORE' => 'Collingwood');
        }

        function findFilter($arg)
        {   
            return $this->filter[$arg[1]];
        }
    }