Hello,
we have web directory script have 50000 links and some links haven't its keywords

1- this is links table structure

CREATE TABLE IF NOT EXISTS `dn_links` (
  `id` int(10) unsigned NOT NULL auto_increment,
  `url` varchar(255) NOT NULL default '',
  `recip` varchar(255) NOT NULL default '',
  `title` varchar(255) NOT NULL default '',
  `description` varchar(255) NOT NULL default '',
  `detail` text NOT NULL,
  `keywords` text NOT NULL,
)  ;

2-we have function to get meta

PHP Code:

function link_submitted_meta($in) {
global $s,$m;
$form = get_meta_tags($in[url]);
$form[url] = $in[url];
if (!$form[title])
{ $x = file($in[url]);
  foreach ($x as $k=>$v)
  { $k = strstr(trim(stripslashes($v)),'<TITLE>'); if (!$k) $k = strstr(trim(stripslashes($v)),'<title>');
    if ($k) { $form[title] = eregi_replace('<title>','',eregi_replace('</title>','',$k)); break; } 
  }
}
$s[subm_all] = 1;
link_submit_form($in[selected_category],$form);
} 


so that we want
php code to check if " keyword filed is empty " > generate keyword automatically by this function
and insert keywords to this field
How we do that ?

Select the rows from the table where the keyword is blank, run the desired data through your function, and then execute an update command to update the row.