Version checker in PHP (for an environment in which get_browser() is unavailable) / You can properly convert a string of version number, often including two or more periods, into a php-readable floating point number.

floatVersion.php

<?php

$agent = getenv('HTTP_USER_AGENT');

function getVersion($req){
  global $agent;
	preg_match(
		"/(?<=".$req."[^0-9\.])([0-9]+)([0-9\._]+?)(?=[^0-9\._]|$)/i",
		$agent,
		$matchedStringsArr
	);
	
	if(! $matchedStringsArr){
		return false;
	}
	
	$matchedStringsArr = str_replace("_", ".", $matchedStringsArr);
	
	if(! strpos($matchedStringsArr[0], '.')){
		return $matchedStringsArr[0];
	}
	
	return $matchedStringsArr[1].'.'.str_replace('.', '', $matchedStringsArr[2]);
}

?>

usage_example.php

<?php

$agent = getenv('HTTP_USER_AGENT');

function getVersion($req){
  global $agent;
  preg_match(
		"/(?<=".$req."[^0-9\.])([0-9]+)([0-9\._]+?)(?=[^0-9\._]|$)/i",
		$agent,
		$matchedStringsArr
	);
  //For example, $matchedStringsArr will be array("10_7_5", "10", "_7_5"), at this time.
  
	if(! $matchedStringsArr){
		return false;
	}
	
	$matchedStringsArr = str_replace("_", ".", $matchedStringsArr);
  //For example, $matchedStringsArr will be array("10.7.5", "10", ".7.5"), at this time.
	
	if(! strpos($matchedStringsArr[0], '.')){
		return $matchedStringsArr[0];
	}
	
	return $matchedStringsArr[1].'.'.str_replace('.', '', $matchedStringsArr[2]);
}

var_dump(array(
$agent,
$osxVer = getVersion("Intel Mac OS X"),
$webkitVer = getVersion("Webkit"),
$chromeVer = getVersion("Chrome"),
$firefoxVer = getVersion("Firefox")
));

/*
* Output Example:

array(5) {
  [0]=>
  string(119) "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_5) AppleWebKit/537.17 (KHTML, like Gecko) Chrome/24.0.1312.52 Safari/537.17"
  [1]=>
  string(5) "10.75"
  [2]=>
  string(6) "537.17"
  [3]=>
  string(10) "24.0131252"
  [4]=>
  NULL
}
*/
?>