Collapsable print_r() tree with PHP 7 (w/o preg_replace() and /e)

Question

In order to print_r a collapsable tree, I\'m currently using his code which uses preg_replace() and the /e modifier, which is depreciated

Answer 1

You need to concat the variable $id value, try this:

function callbackFunction($matches) {
    $id = substr(md5(rand().$matches[0]), 0, 7);
    return "$matches[1]<a href=\"javascript:toggleDisplay('$id');\">$matches[2]</a><div id='$id' style=\"display: none;\">'";
}