$re = '/(?=\. [a-z1-9\. ]*?com/)\. /m';
$str = 'Eastern Illinois University is one of only three universities in the United States to run its own newspaper printing press http://www. dailytexanonline. com/top-stories/student-media-board-votes-to-sell-press-1.1309992 and is one of the smallest universities in the country to have a daily newspaper. The paper was renamed Teacher\'s College News and Eastern State News before its current name was chosen in 1980. http://media. www. dennews. com/media/storage/paper309/news/2005/11/04/News/The-News. Turns.90-1045667. shtml Notable alumni of the newspaper include Wall Street Journal reporter Cam Simpson';
$subst = ".";
$result = preg_replace($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