$re = '/SSR.(....)(.BE.)(\w+)(-1)(\w+)(\/)(\w+).*/m';
$str = 'SSR BAGW BE HK1DUBEXT0304H13OCT-1TIMBRELL/TEGAELAMISS.1P/AUTH 23KG
SSR BAGA BE HK1DUBLON0301H13NOV-1TIMBRELL/TEGAELAMISS.1P/AUTH 23KG
SSR DOCS BE HK1DUBEXT0204H13DEC-1TIMBRELL/TEGAELAMISS
SSR PETC BE HK1LONEXT0334H13JAN-1TIMBRELL/TEGAELAMISS
SSR WCHR BE HK1DUBEXT0204H13DEC-1TIMBRELL/TEGAELAMISS
SSR BAGW BE HK1DUBLON0301H13NOV-1TIMBRELL/TEGAELAMISS.1P/AUTH 23KG
BE7351 H 08NOV18MANMXP HK4/11251440
BE2108R/VS8508Y 11NOV18LHREDI HK10/18202000
A97351 H 08NOV18MANMXP HK4/11251440';
$subst = "\1-\5-\7";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
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