$re = '~ABC\h*\d+\h*DEF\h*\d+\h*GHI~m';
$str = '1. ABC 1111111111 DEF 222222222 GHI
2. ABC 3333333 DEF 33333333 GHI
3. И т.д.';
$subst = "слово";
$result = preg_replace($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