PHP change table name to lowcase

$subject = "From ab_cD efg";

$callback = function($match)

{

    //var_dump($match);

    //echo $match[1];

    return "FROM " . strtolower($match[1]) . " ";

    //return preg_replace($match[1], strtolower($match[1]) ,$match[0]);

};

echo preg_replace_callback('/from\s+([\w]+)\s*/i', $callback, $subject, 1);

 echo "\n";

echo preg_replace_callback('/from\s+([\w]+)\s*/i', $callback, "From ab_cD", 1);

 echo "\n";

echo preg_replace_callback('/from\s+([\w]+)\s*/i', $callback, "Fsssc ab_cD", 1);

ref

http://tools.jb51.net/regex/create_reg

// 将文本中的年份增加一年.

$text = "April fools day is 04/01/2002n";

$text.= "Last christmas was 12/24/2001n";

// 回调函数

function next_year($matches)

{

  // 通常: $matches[0]是完成的匹配

  // $matches[1]是第一个捕获子组的匹配

  // 以此类推

  return $matches[1].($matches[2]+1);

}

echo preg_replace_callback(

            "|(d{2}/d{2}/)(d{4})|",

            "next_year",

            $text);