How do you integrate an external API into WordPress?

1. Understand the API

• Get the API documentation (base URL, endpoints, authentication method).
• Check if it uses REST or GraphQL.
• Note required API keys or tokens.

2. Choose Where to Integrate

You can integrate API calls in:

• Theme functions (functions.php)
• Custom plugin (recommended for reusability)
• Custom REST endpoint for AJAX/frontend usage

3. Make the API Request

WordPress provides HTTP functions:

• wp_remote_get() for GET requests
• wp_remote_post() for POST requests

Example – GET request:

function get_weather_data() {
    $response = wp_remote_get( 'https://api.example.com/weather?city=London', array(
        'headers' => array(
            'Authorization' => 'Bearer YOUR_API_KEY'
        )
    ));

    if ( is_wp_error( $response ) ) {
        return 'Error fetching data';
    }

    $body = wp_remote_retrieve_body( $response );
    return json_decode( $body, true );
}

4. Display the Data

Example in a shortcode:

function display_weather_shortcode() {
    $data = get_weather_data();
    if ( isset( $data['temperature'] ) ) {
        return 'Temperature: ' . esc_html( $data['temperature'] ) . '°C';
    }
    return 'No data available';
}
add_shortcode( 'weather', 'display_weather_shortcode' );

Usage in a post/page:

[weather]

5. Handle Authentication

• API Key in URL → Add as query parameter.
• Bearer Token → Use Authorization header.
• OAuth → Implement token retrieval & refresh logic.

6. Cache API Responses

External APIs may have request limits — use transients to store responses temporarily:

function get_cached_weather() {
    $data = get_transient( 'weather_data' );
    if ( false === $data ) {
        $data = get_weather_data();
        set_transient( 'weather_data', $data, HOUR_IN_SECONDS );
    }
    return $data;
}

✅ Best Practices

• Sanitize & escape all output.
• Use caching to reduce API calls.
• Handle errors gracefully.
• Never expose API keys in public JS — call APIs from server-side PHP.

💡 Analogy:
Integrating an API into WordPress is like hiring a courier service — your site requests information from somewhere else, waits for the delivery, and then displays it to visitors.