PHP mysqli_connect() Function: Usage and Examples

Opens a MySQL database connection with host, account and database credentials.

The examples focus on the operation itself, including the important distinction: mysqli_real_connect completes a connection created with mysqli_init.

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_connect(...) — 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

Read credentials from server-side configuration. Connection errors should be logged privately in production.

<?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');
echo mysqli_get_host_info($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

Read credentials from server-side configuration. Connection errors should be logged privately in production. A connected handle provides server and charset metadata.

<?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');
echo mysqli_get_server_info($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

Read credentials from server-side configuration. Connection errors should be logged privately in production. A connected handle provides server and charset metadata.

<?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');
echo mysqli_character_set_name($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

Avoid exposing passwords or connection errors to a public page; set the charset after connection.

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

• Opens a MySQL database connection with host, account and database credentials.
• Avoid exposing passwords or connection errors to a public page; set the charset after connection.
• mysqli_real_connect completes a connection created with mysqli_init.

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