Need help with insert form

[fagin]

Hi,

I have the insert form below which works just fine except for the if else condition.
If the name already exists, i'd like it to echo name already exists.
I know that I am doing something wrong. Can someone help?
Thanks much !

if(isset($_REQUEST['add_group']))
{



$result_content = mysql_query ("SELECT * FROM $table_group WHERE first_name = '" . $first_name. "' limit 1 ");

if ( mysql_num_rows($result_content)==0){

$sql="INSERT INTO $table_group (first_name, last_name)VALUES('$first_name', '$last_name')"; }else { echo  "Name already exists"; }

$result=mysql_query($sql);

// if successfully insert data into database, displays message "Successful".
if($result){
echo "Successful";
echo "<BR>";
echo "<a href='insert.php'>Back to main page</a>";
}

else {
echo "ERROR";
}
}
// close connection
mysql_close();


?>

<table width="300" border="0" align="center" cellpadding="0" cellspacing="1">
<tr>
<td><form name="form1" method="post" action="insertTest.php">
  
<?php

    if (isset($data_content["first_name"]) and
            $data_content["first_name"] != '' and
            !isset($_POST['first_name'])) {
        $first_name = $data_content["first_name"];
    } elseif (isset($_POST['first_name'])) {
        $first_name = $_POST['first_name'];
    } else {
        $first_name = '';
    } 
    $first_name = htmlentities(stripslashes($first_name), ENT_QUOTES, $character_set);

    if (isset($data_content["last_name"]) and
            $data_content["last_name"] != '' and
            !isset($_POST['last_name'])) {
        $last_name = $data_content["last_name"];
    } elseif (isset($_POST['last_name'])) {
        $last_name = $_POST['last_name'];
    } else {
        $last_name = '';
    } 
    $last_name = htmlentities(stripslashes($last_name), ENT_QUOTES, $character_set);
?>

<table width="100%" border="0" cellspacing="1" cellpadding="3">
<tr>
<td colspan="3"><strong>Insert Data Into mySQL Database </strong></td>
</tr>
<tr>
<td width="71">First name</td>
<td width="6">:</td>
<td width="301"><input name="first_name" type="text" id="first_name" value="<?php echo $first_name ?>"></td>
</tr>
<tr>
<td>Lastname</td>
<td>:</td>
<td><input name="last_name" type="text" id="last_name" value="<?php echo $last_name ?>"></td>
</tr>

<tr>
<td colspan="3" align="center"><input type="submit" name="add_group" value="Submit"></td>
</tr>
</table>
</form>
</td>
</tr>
</table>