$re = '/(?<=^|,)[789](?=,|$)/m';
$str = '7,30 IN, Ball Valve,9Trunnion,9, CL 900, BW, Body LTCS, Metal Seat, Gear Operated,37,7, NACE MR 0175/ISO 15156 -with extended pup-piece as pipe schedule. VBFW 91Z08.75 IN,77, Gen manu,7 2500, Flanged,7, Body DSS,8, Trim DSS,75, Ball Valve,9, CL 2500,99, RF,Swing Body DSS,789, Trim DSS, Reduced Bore -770343.254.1,9';
preg_match_all($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