PHP Regular expression

I need to add href=" before an http:// if this http:// doesn't follow href=" or src="

Following code partly works. Partly means it considers <a href=" only but not src="

$str= preg_replace( 
    "/(?<!a href=\")((http|ftp)+(s)?:\/\/[^<>\s]+)/i", 
    "<a href=\"\\0\"> target=\"blank\">\\0</a>", 
    $str
);

Thank you guys in advance for your reply.

From stackoverflow

• $str= preg_replace( 
      "/(?<!a href=\")(?<!src=\")((http|ftp)+(s)?:\/\/[^<>\s]+)/i", 
      "<a href=\"\\0\"> target=\"blank\">\\0</a>", 
      $str
  );
  

  David : works well. Thank you.