$re = '/^\d{4}\s+\d{2}([A-Z ]*?[A-Z])\s*\d.*/m';
$str = '0010 00LTT BOX PCS RH039349 0101113140 DE1 D 1
1210 02EXH BX PCS RH 060644 010111 DL5 D 1
0010 00PLATE BENT 039348 0101116201 DE1 B 1
0010 00PLATE BENT RH 039348 0101116201 DE1 C 1
0010 00ANGLE 038310 0101110200 DD1 B 1';
$subst = "$1";
$result = preg_replace($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