Update as NULL Mysql - php

Question

<form action="hi.php" method="post">
<input type="text" name="id" />
<input type="hidden" name="name" value="name" />
</form>
I send this input with no value. I want to update id column as NULL.
$id = $_POST['id'];
$name = $_POST['name'];
$mysqli->query("UPDATE table SET id=$id WHERE name='$name');
However that updates it as empty not NULL. How I can insert NULL in $id?
If I send a value with <input name="id">, it updates it correctly. However if I send it empty, column becomes empty, I want it as NULL.

Answer 1

When using prepared statements and parameters, a NULL value in one of the parameters will also be treated as NULL by the MySQL server.
HTTP parameters are transported as strings. If no value has been given for an input control, the value for the key/value-pair will be an empty string (!=NULL). But you can still have somethig like if(emptystring) use NULL in your script.
e.g.
<?php
// only for this example; otherwise leave _POST alone....
$_POST['id'] = 1;
$_POST['name'] = '';
$mysqli = new mysqli('localhost', 'localonly', 'localonly', 'test');
if ($mysqli->connect_errno) {
trigger_error( sprintf('mysqli connect error (%d) %s', $mysqli->connect_errno, $mysqli->connect_error), E_USER_ERROR);
die;
}
mysqli_report(MYSQLI_REPORT_STRICT|MYSQLI_REPORT_ALL); // that's all the "error handling" for this example....
setup($mysqli);
// even if the user didn't fill in any value, the parameters should be in the request
// as empty strings
if ( !isset($_POST['name'], $_POST['id']) ) {
echo 'missing POST paramete';
}
else {
// <-- maybe some plausiblity checks here anyway; e.g. some assumptions about the id you can test, leaving it out as optional for now --->
// decision point: applying trim() to _POST[name] and _then_ consider it NULL or not - you might disagree about the specifics, just an example.
$name = trim($_POST['name']);
if ( 0===strlen($name) ) {
$name = NULL;
}
// <-- actually it would suffice to establish the databse connection here....
$stmt = $mysqli->prepare('UPDATE soFoo set name=? WHERE id=?');
$stmt->bind_param('ss', $name, $_POST['id']);
$stmt->execute();
printTable($mysqli);
}
function printTable($mysqli) {
$result = $mysqli->query('SELECT * FROM soFoo ORDER BY id');
foreach( $result as $row ) {
var_export($row); echo "\r\n";
}
}
function setup($mysqli) {
$mysqli->query('CREATE TEMPORARY TABLE soFoo (id int, name varchar(32), primary key(id))');
$mysqli->query("INSERT INTO soFoo (id,name) VALUES(1,'oldname1'),(2,'oldname2')");
}
prints
array (
'id' => '1',
'name' => NULL,
)
array (
'id' => '2',
'name' => 'oldname2',
)

Answer 2

I suggest you use PDO, and not mysql() but this will give you the idea:
$id = $_POST['id'];
if($id==''){
$id='NULL';
}
else{
$id = mysql_real_escape_string($id);
}
$qr = 'Update table SET id='.$id;
mysql_query($qr);