$re = '/(\s*)(19[5-9]\d|20[0-4]\d)(?:\s*-\s*(19[5-9]\d|20[0-4]\d))?(?=\s)/m';
$str = '2007 Chevy Silverado Pickup new body style models 2008-2013 Chevy Silverado All Models 2014 Chevy Silverado 2500HD 3500HD 2007 GMC Sierra Pickup new body style models 2008 - 2013 GMC Sierra All Models 2014 GMC Sierra 2500HD 3500HD 2007-2013 Chevy Tahoe 2007-2013 Chevy Suburban 2007 - 2013 Chevy Avalanche 2007-2013 GMC Yukon Yukon XL Yukon Denali';
preg_match_all($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