$re = '/^(?:0*(?:[0-9]|[1-9][0-9][0-9]?|[1-4][0-9][0-9][0-9])(?:[.][0-9])?|5000(?:[.]0)?)$/m';
$str = '5000
4999.9
25.0
2500.9
0.4
5000.5
5000.0';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php