Email+URL judgment and automatic conversion function_PHP tutorial

function validateEmail($email)  
{     return eregi("^[_a-z0-9-]+(.[_a-z0-9-]+)*@[a-z0-9-]+(.[a-z0-9-]+)*(.[a-z]{2,3})$", $email);  
}  

function validateURL($url)  
{     return eregi("^((ht|f)tp://)((([a-z0-9-]+(.[a-z0-9-]+)*(.[a-z]{2,3}))|(([0-9]{1,3}.){3}([0-9]{1,3})))((/|?)[a-z0-9~#%&'_+=:?.-]*)*)$", $url);  
}  

function convertURLS($text)  
{     $text = eregi_replace("((ht|f)tp://www.|www.)([a-z0-9-]+(.[a-z0-9-]+)*(.[a-z]{2,3})((/|?)[a-z0-9~#%&\/'_+=:?.-]*)*)", "http://www.\3", $text);  
    $text = eregi_replace("((ht|f)tp://)((([a-z0-9-]+(.[a-z0-9-]+)*(.[a-z]{2,3}))|(([0-9]{1,3}.){3}([0-9]{1,3})))((/|?)[a-z0-9~#%&'_+=:?.-]*)*)", "\0", $text);  
    return $text;  
}  

function convertMail($text)  
{     $text = eregi_replace("([_a-z0-9-]+(.[_a-z0-9-]+)*@[a-z0-9-]+(.[a-z0-9-]+)*(.[a-z]{2,3}))", "\0", $text);  
    return $text;  
}  

function convertAllLinks($text)  
{     $text = convertURLS($text);  
    $text = convertMail($text);  
    return $text;  
}
?>