Php MySQL update html form - php

Question

There is a table:
|id name surname email |
|1 john surjohn #mail.com|
|2 peter pet #mail.com|
|.........................|
PHP:
<?php
if(isset($_POST['update']))
{
...
$conn = mysql_connect($dbhost, $dbuser, $dbpass);
if(! $conn )
{
die('Could not connect: ' . mysql_error());
}
$id = $_POST['id'];
$name = $_POST['name'];
$surname = $_POST['surname'];
$mail = $_POST['mail'];
$sql = "UPDATE emps ".
"SET name= '$name', surname'$surname', email='$mail' ".
"WHERE Id = $id" ;
mysql_select_db('dbase');
$retval = mysql_query( $sql, $conn );
if(! $retval )
{
die('Could not update data: ' . mysql_error());
}
echo "blablablabla ! \n";
mysql_close($conn);
}
else
{
?>
<form method="post" action="<?php $_PHP_SELF ?>">
<fieldset style="width: 350px" >
<table width="400" border="0" cellspacing="1" cellpadding="2">
<tr>
<td width="100">Id </td>
<td><input name="id" type="text" id="id" value=""></td>
</tr>
<tr>
<td width="100">name</td>
<td><input type="text" maxlength="15" name="name" value="" ></td>
</tr>
<tr>
<td width="100">surname</td>
<td><input type="text" maxlength="40" name="surname" value="" ></td>
</tr>
<tr>
<td width="100"> </td>
<td>
<input name="update" type="submit" id="update" value="update">
</td>
</tr>
</table>
</fieldset>
</form>
<?php
}
?>
}
In this form i need update all fields otherwise, updated table can have null values.
I want for example, update name field, but leave surname, email existing values. ideas?

Answer 1

Could try something like this:
$id = $_POST['id'];
$name = $_POST['name'];
$surname = $_POST['surname'];
$mail = $_POST['mail'];
$sql = "UPDATE emps SET";
$moresql = '';
if(isset($name) && !empty($name)) {
$moresql .= " name = '$name'";
}
if(isset($surname) && !empty($surname)) {
if ($moresql) $moresql .= ',';
$moresql .= " surname = '$surname'";
}
if(isset($mail) && !empty($mail)) {
if ($moresql) $moresql .= ',';
$moresql .= " mail = '$mail'";
}
$sql .= $moresql;
$sql .= " WHERE Id = '$id'";
This is untested though.

Answer 2

Karl's idea is the way to go, but it can be refactored this way:
$id = $_POST['id'];
$sql = "UPDATE emps SET";
$fieldValuePairs = array();
foreach($_POST as $key => value)
if($key != 'id')
$fieldValuePairs[] = "'$key' = '$value'";
$sql .= " ". implode(',', $fieldValuePairs)." WHERE id = $id";
Note: this works only if you use input names (in the form) equal the column names (in the database).
Have a great day.