PHP mysqli_close() Function: Usage and Examples

Closes an active MySQLi connection.

The examples focus on the operation itself, including the important distinction: mysqli_connect creates a connection.

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_close(...) — 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

Once closed, do not reuse the same handle for queries.

<?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');
mysqli_close($link);
echo "Connection closed";

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

Example 2: Checking Behavior

Once closed, do not reuse the same handle for queries. Closing a handle ends its use for further queries.

<?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');
mysqli_close($link);
echo "mysqli handle released";

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

Example 3: Practical Example

Once closed, do not reuse the same handle for queries. Closing a handle ends its use for further queries.

<?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');
mysqli_close($link);
echo "Done with this DB connection";

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

Result sets and statements should no longer be used after the connection closes.

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

• Closes an active MySQLi connection.
• Result sets and statements should no longer be used after the connection closes.
• mysqli_connect creates a connection.

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