PHP mysqli_insert_id() Function: Usage and Examples

Reports the auto-generated ID from the previous INSERT on this connection.

The examples focus on the operation itself, including the important distinction: PDO::lastInsertId is the PDO equivalent.

What It Does

Use the examples below to observe the behavior on a small dataset before extending it to application code.

Syntax and Return Value

mysqli_insert_id(...) — requires the corresponding optional extension

The displayed signature describes the API or identifies any correction or optional dependency. When a parameter is optional, supply it only when the task requires it.

Example 1: Basic Use

Examples assume a demo database containing users(id, email, active), products(id, name, price), and orders(id, user_id, total) as required by the query. A unique constraint on users.email should protect duplicates.

<?php
$link = mysqli_connect(getenv('DB_HOST') ?: '127.0.0.1', getenv('DB_USER') ?: 'app', getenv('DB_PASSWORD') ?: '', getenv('DB_NAME') ?: 'demo');
mysqli_set_charset($link, 'utf8mb4');
$email = '[email protected]';
$stmt = mysqli_prepare($link, "INSERT INTO users(email, active) VALUES (?, 1)");
mysqli_stmt_bind_param($stmt, "s", $email);
mysqli_stmt_execute($stmt);
echo mysqli_insert_id($link);

This example is meant for a configured application environment; output depends on the installed extension, external service, or database contents.

Example 2: Checking Behavior

Examples assume a demo database containing users(id, email, active), products(id, name, price), and orders(id, user_id, total) as required by the query. A unique constraint on users.email should protect duplicates.

<?php
$link = mysqli_connect(getenv('DB_HOST') ?: '127.0.0.1', getenv('DB_USER') ?: 'app', getenv('DB_PASSWORD') ?: '', getenv('DB_NAME') ?: 'demo');
mysqli_set_charset($link, 'utf8mb4');
$email = '[email protected]';
$stmt = mysqli_prepare($link, "INSERT INTO users(email, active) VALUES (?, 1)");
mysqli_stmt_bind_param($stmt, "s", $email);
mysqli_stmt_execute($stmt);
echo mysqli_insert_id($link);

This example is meant for a configured application environment; output depends on the installed extension, external service, or database contents.

Example 3: Practical Example

Examples assume a demo database containing users(id, email, active), products(id, name, price), and orders(id, user_id, total) as required by the query. A unique constraint on users.email should protect duplicates.

<?php
$link = mysqli_connect(getenv('DB_HOST') ?: '127.0.0.1', getenv('DB_USER') ?: 'app', getenv('DB_PASSWORD') ?: '', getenv('DB_NAME') ?: 'demo');
mysqli_set_charset($link, 'utf8mb4');
$email = '[email protected]';
$stmt = mysqli_prepare($link, "INSERT INTO users(email, active) VALUES (?, 1)");
mysqli_stmt_bind_param($stmt, "s", $email);
mysqli_stmt_execute($stmt);
echo mysqli_insert_id($link);

This example is meant for a configured application environment; output depends on the installed extension, external service, or database contents.

Important Behavior and Edge Cases

Zero may mean no generated ID; this does not replace fetching the inserted record.

This API is supplied by an optional extension that is not installed in the local test runtime, or requires a different PHP version. The example must be verified in a matching environment.

Comparison with Related Approaches

Common Beginner Mistakes

Key Takeaways

• Reports the auto-generated ID from the previous INSERT on this connection.
• Zero may mean no generated ID; this does not replace fetching the inserted record.
• PDO::lastInsertId is the PDO equivalent.

Use mysqli_insert_id when its documented behavior matches the problem. Test the relevant edge cases in your own runtime before deploying it.