<?php
$vars=array();
 
$vars['peremena'] = 33; //переменная для замены
$vars['code'] = 'smart'; //переменная для замены
 
$php_codes = array( //собственно сами условия замены
    "\[php\](.+)\[/php\]" => "$1"
);
 
$tpl_file = [
'Hello [php]peremena[/php], ',
'Bye [php]code[/php] code'
];
 
$myMatch=function($match) use ($vars) {
       	return $vars[$match[1]];
};
 
 
foreach ($tpl_file as $line_num => $line){ //построчный вывод файла
    foreach ($php_codes as $key => $php_code) //сам парсер
        $line = preg_replace_callback("#".$key."#isU", $myMatch, $line); //замена текста на переменную, имя которой содержится в $php_code
 
    echo $line; //вывод строки
}
// your code goes here

PD9waHAKJHZhcnM9YXJyYXkoKTsKCiR2YXJzWydwZXJlbWVuYSddID0gMzM7IC8v0L/QtdGA0LXQvNC10L3QvdCw0Y8g0LTQu9GPINC30LDQvNC10L3RiwokdmFyc1snY29kZSddID0gJ3NtYXJ0JzsgLy/Qv9C10YDQtdC80LXQvdC90LDRjyDQtNC70Y8g0LfQsNC80LXQvdGLCgokcGhwX2NvZGVzID0gYXJyYXkoIC8v0YHQvtCx0YHRgtCy0LXQvdC90L4g0YHQsNC80Lgg0YPRgdC70L7QstC40Y8g0LfQsNC80LXQvdGLCiAgICAiXFtwaHBcXSguKylcWy9waHBcXSIgPT4gIiQxIgopOwoKJHRwbF9maWxlID0gWwonSGVsbG8gW3BocF1wZXJlbWVuYVsvcGhwXSwgJywKJ0J5ZSBbcGhwXWNvZGVbL3BocF0gY29kZScKXTsKCiRteU1hdGNoPWZ1bmN0aW9uKCRtYXRjaCkgdXNlICgkdmFycykgewogICAgICAgCXJldHVybiAkdmFyc1skbWF0Y2hbMV1dOwp9OwoKCmZvcmVhY2ggKCR0cGxfZmlsZSBhcyAkbGluZV9udW0gPT4gJGxpbmUpeyAvL9C/0L7RgdGC0YDQvtGH0L3Ri9C5INCy0YvQstC+0LQg0YTQsNC50LvQsAogICAgZm9yZWFjaCAoJHBocF9jb2RlcyBhcyAka2V5ID0+ICRwaHBfY29kZSkgLy/RgdCw0Lwg0L/QsNGA0YHQtdGACiAgICAgICAgJGxpbmUgPSBwcmVnX3JlcGxhY2VfY2FsbGJhY2soIiMiLiRrZXkuIiNpc1UiLCAkbXlNYXRjaCwgJGxpbmUpOyAvL9C30LDQvNC10L3QsCDRgtC10LrRgdGC0LAg0L3QsCDQv9C10YDQtdC80LXQvdC90YPRjiwg0LjQvNGPINC60L7RgtC+0YDQvtC5INGB0L7QtNC10YDQttC40YLRgdGPINCyICRwaHBfY29kZQoKICAgIGVjaG8gJGxpbmU7IC8v0LLRi9Cy0L7QtCDRgdGC0YDQvtC60LgKfQovLyB5b3VyIGNvZGUgZ29lcyBoZXJl