PDO get the last ID inserted

I have a query, and I want to get the last ID inserted. The field ID is the primary key and auto incrementing.

I know that I have to use this statement:

LAST_INSERT_ID()

That statement works with a query like this:

$query = "INSERT INTO `cell-place` (ID) VALUES (LAST_INSERT_ID())";

But if I want to get the ID using this statement:

$ID = LAST_INSERT_ID();

I get this error:

Fatal error: Call to undefined function LAST_INSERT_ID()

What am I doing wrong?

That's because that's an SQL function, not PHP. You can use PDO::lastInsertId().

Like:

$stmt = $db->prepare("...");
$stmt->execute();
$id = $db->lastInsertId();

If you want to do it with SQL instead of the PDO API, you would do it like a normal select query:

$stmt = $db->query("SELECT LAST_INSERT_ID()");
$lastId = $stmt->fetchColumn();

lastInsertId() only work after the INSERT query.

Correct:

$stmt = $this->conn->prepare("INSERT INTO users(userName,userEmail,userPass) 
                              VALUES(?,?,?);");
$sonuc = $stmt->execute([$username,$email,$pass]);
$LAST_ID = $this->conn->lastInsertId();

Incorrect:

$stmt = $this->conn->prepare("SELECT * FROM users");
$sonuc = $stmt->execute();
$LAST_ID = $this->conn->lastInsertId(); //always return string(1)=0

You can get the id of the last transaction by running lastInsertId() method on the connection object($conn).

Like this $lid = $conn->lastInsertId();

Please check out the docs https://www.php.net/manual/en/language.oop5.basic.php