Grab, strip and dump out phpinfo() into part of a page, neutering some of its overriding HTML and styles.

phpinfo-dump.php

ob_start();
phpinfo();
$phpInfo = ob_get_clean();

$phpInfo = preg_replace('/600(px)?/', '100%', $phpInfo); // table and hr width
$phpInfo = str_replace('75%', '95%', $phpInfo); // font-size
$phpInfo = preg_replace('/<?([\w]|<|\/|>)*(a:|!DOCTYPE|<html|title|body)(.+)?\\n?/', '', $phpInfo); // main html doc tags

For PHP 5.6:

ob_start();
phpinfo();
$php_info = ob_get_clean();
$php_info = preg_replace('/934(px)?/', '100%', $php_info);
preg_match('#().*(.*)#s', $php_info, $matches);
echo $matches[1];

echo $matches[2];