[ Posted by ARUN AK ] Links update in a give text.

fiddle_016838.php

<?php

$string = "Hallo Studenten http://google.com/your/subpage and https://www.yahoo.com/my/subpage";
  $regexp = "/\b(?:(?:https?|ftp):\/\/|www\.)[-a-z0-9+&@#\/%?=~_|!:,.;]*[-a-z0-9+&@#\/%=~_|]/i";
  $anchorMarkup = "<a href=\"%s://%s\" target=\"_blank\" >%s</a>";

  preg_match_all($regexp, $string, $matches, \PREG_SET_ORDER);
  echo '<pre>';print_r($matches);echo '</pre>';
  foreach ($matches as $match) {
    if (empty($match[1]) && empty($match[7])) {
      $http = $match[2]?$match[2]:'http';
      $replace = sprintf($anchorMarkup, $http, $match[0], $match[0], $match[1]);
      $string = str_replace($match[0], $replace, $string);
    }
  }
  echo $string; 
?>