Version 2.4 | Last updated: September 2026

This document provides a complete reference for integrating with the Metrici LPR (License Plate Recognition) system. The API allows you to query plate detections, manage access control lists (ACL), handle groups, and manage parking operations.

Table of Contents

• Quick Start
• Authentication
• Common Parameters
• Response Format
• Plate Detection & History
  • List Detected Plates
  • Search by Plate Number
  • Last Car Detected
  • Last Car with Live View
  • Detection Statistics
• Actions / ACL Management
  • List All Actions
  • Insert Action (Add Plate to ACL)
  • Delete Action by Plate Number
  • Delete Action by ID
  • Delete Expired Actions
• General
  • Get Cameras
  • Get Locations
  • Get Timetables
• Groups
  • List All Groups
  • Create Group
  • Update Group
  • Delete Group
  • List Plates in Group
  • Add Plate to Group (Inherit Settings)
  • Add Plate to Group (Custom Expiry)
• Parking
  • Cars Inside Location
  • Parking Events
  • Get Parking Price
  • Get Plate Numbers Inside
  • Set Paid Amount
  • Parking Spaces by Tenant
  • Parking Statistics
  • Tenant Cars
  • Event Confirmation
• Error Handling
• Webhooks / Callbacks
• Image URLs

Quick Start

1. Get your API key from the Metrici LPR admin panel.
2. Generate the auth token for each request using MD5 hashing.
3. Make HTTP GET requests to the API endpoints.

Minimal Example (cURL)

# Step 1: Generate auth token
# auth = md5(plate_number + api_key)
AUTH=$(echo -n "BV01ABC${API_KEY}" | md5sum | awk '{print $1}')

# Step 2: Make the request
curl "https://YOUR_HOST/api/lpr/search.php?plate=BV01ABC&auth=${AUTH}&output=json"

Authentication

All API endpoints (except delete_expired.php and event_confirmation.php) require an auth parameter.

How to Generate the Auth Token

The auth token is an MD5 hash computed as follows:

auth = md5(to_concat + api_key)

Where:

• api_key — your secret API key (from the admin panel)
• to_concat — a concatenation of specific request parameters, in a specific order (varies per endpoint)

Auth Token Generation Per Endpoint

PHP Example

$api_key = 'YOUR_API_KEY';
$plate_number = 'BV01ABC';
$auth = md5($plate_number . $api_key);

Python Example

import hashlib

api_key = 'YOUR_API_KEY'
plate_number = 'BV01ABC'
auth = hashlib.md5((plate_number + api_key).encode()).hexdigest()

JavaScript Example

// Node.js
const crypto = require('crypto');
const api_key = 'YOUR_API_KEY';
const plate_number = 'BV01ABC';
const auth = crypto.createHash('md5').update(plate_number + api_key).digest('hex');

Common Parameters

Response Format

JSON (default)

Success Response:

{
  "error": false,
  "response": {
    "header": {
      "count": 3,
      "duration": "0.05"
    },
    "body": [
      {
        "id": 1234,
        "plate_number": "BV01ABC",
        "probability": 95.5,
        "country": "Romania",
        "seen": "2025-07-15 14:30:00",
        "camera_id": 1,
        "camera_description": "Camera Entrance",
        "plate_snapshot": "http://YOUR_HOST/live/plate_image.php?id=1234",
        "car_snapshot": "http://YOUR_HOST/live/car_image.php?id=1234"
      }
    ]
  }
}

Error Response:

{
  "error": true
}

Error with Message:

{
  "error": true,
  "message": "Incorrect authorization key."
}

XML

When output=xml, the response is formatted as XML with <plate> elements in the body.

Plate Detection & History

List Detected Plates

Get a list of all detected plates within a date range, optionally filtered by camera.

Endpoint: GET /api/lpr/list.php

Parameters:

Response Body Fields:

Example:

curl "https://YOUR_HOST/api/lpr/list.php?start=2025-07-01&end=2025-07-15&auth=${AUTH}&output=json"

Search by Plate Number

Search for a specific plate number within a date range.

Endpoint: GET /api/lpr/search.php

Parameters:

Response Body Fields: Same as List Detected Plates

Example:

AUTH=$(echo -n "BV01ABC${API_KEY}" | md5sum | awk '{print $1}')
curl "https://YOUR_HOST/api/lpr/search.php?plate=BV01ABC&start=2025-07-01&auth=${AUTH}&output=json"

Last Car Detected

Get the most recently detected car(s), optionally filtered by camera. Returns the latest detection per camera.

Endpoint: GET /api/lpr/last_car.php

Parameters:

Response Body Fields:

Example:

curl "https://YOUR_HOST/api/lpr/last_car.php?camera_id=1,2&auth=${AUTH}&output=json"

Last Car with Live View

Same as Last Car Detected but includes a live camera snapshot and only returns plates above the configured minimum probability threshold.

Endpoint: GET /api/lpr/last_car_liveview.php

Parameters:

Additional Response Fields (beyond last_car.php):

Example:

curl "https://YOUR_HOST/api/lpr/last_car_liveview.php?camera_id=1&auth=${AUTH}&output=json"

Detection Statistics

Get total and unique car counts for a date range.

Endpoint: GET /api/lpr/stats.php

Parameters:

Response:

{
  "error": false,
  "response": {
    "header": {
      "camera_id": null,
      "count": 150,
      "duration": "0.12"
    },
    "body": {
      "total_cars": 150,
      "unique_cars": 87
    }
  }
}

Example:

curl "https://YOUR_HOST/api/lpr/stats.php?start=2025-07-01&end=2025-07-15&auth=${AUTH}&output=json"

Actions / ACL Management

The ACL (Access Control List) system manages which plates are recognized and what actions are triggered when they are detected (e.g., open barrier, send email, show popup).

List All Actions

Get all configured ACL entries.

Endpoint: GET /api/lpr/actions.php

Parameters: None (besides auth and output)

Response Body Fields:

Example:

curl "https://YOUR_HOST/api/lpr/actions.php?auth=${AUTH}&output=json"

Insert Action (Add Plate to ACL)

Add a plate number to the ACL. The plate will have barrier opening enabled by default.

Endpoint: GET /api/lpr/insert_action.php

Parameters:

Response:

{
  "error": false,
  "message": "Plate ACL successfully inserted.",
  "id": 42,
  "access_code": "12345678"
}

Error Responses:

Example:

# Add plate BV01ABC to all cameras, no expiry
AUTH=$(echo -n "BV01ABCadd1" | md5sum | awk '{print $1}')
curl "https://YOUR_HOST/api/lpr/insert_action.php?plate_number=BV01ABC&action=add&auth=${AUTH}&output=json"

# Add plate BV01ABC to camera 1, expiring in 24 hours
EXPIRE=$(date -d '+24 hours' +%s)
AUTH=$(echo -n "BV01ABCadd1${EXPIRE}" | md5sum | awk '{print $1}')
curl "https://YOUR_HOST/api/lpr/insert_action.php?plate_number=BV01ABC&action=add&camera_id=1&expire=${EXPIRE}&auth=${AUTH}&output=json"

# Add plate BV01ABC with a custom access code and email (concat order: plate_number + action + access_code + access_code_email_address)
AUTH=$(echo -n "BV01ABCadd01234567john.doe@example.com" | md5sum | awk '{print $1}')
curl "https://YOUR_HOST/api/lpr/insert_action.php?plate_number=BV01ABC&action=add&access_code=01234567&access_code_email_address=john.doe@example.com&auth=${AUTH}&output=json"

Delete Action by Plate Number

Remove a plate from the ACL.

Endpoint: GET /api/lpr/delete_action.php

Parameters:

Response:

{
  "error": false,
  "message": "Plate ACL successfully deleted."
}

Example:

AUTH=$(echo -n "BV01ABC" | md5sum | awk '{print $1}')
curl "https://YOUR_HOST/api/lpr/delete_action.php?plate_number=BV01ABC&auth=${AUTH}&output=json"

Delete Action by ID

Remove an ACL entry by its database ID.

Endpoint: GET /api/lpr/delete_action_by_id.php

Parameters:

Response:

{
  "error": false,
  "message": "Plate ACL successfully deleted."
}

Example:

AUTH=$(echo -n "42" | md5sum | awk '{print $1}')
curl "https://YOUR_HOST/api/lpr/delete_action_by_id.php?id=42&auth=${AUTH}&output=json"

Delete Expired Actions

Remove all ACL entries that have passed their expiration date. This endpoint does not require authentication.

Endpoint: GET /api/lpr/delete_expired.php

Parameters: None

Response: Plain text: Expired Plates ACL deleted

Example:

# Can be used in a cron job
curl "https://YOUR_HOST/api/lpr/delete_expired.php"

General

Get Cameras

List all configured cameras.

Endpoint: GET /api/lpr/general/get_cameras.php

Parameters:

Response Body Fields:

Example:

curl "https://YOUR_HOST/api/lpr/general/get_cameras.php?auth=${AUTH}&output=json"

Get Locations

List all configured locations.

Endpoint: GET /api/lpr/general/get_locations.php

Parameters: None (besides auth and output)

Response Body Fields:

Example:

curl "https://YOUR_HOST/api/lpr/general/get_locations.php?auth=${AUTH}&output=json"

Get Timetables

List all configured timetables (used for scheduling ACL actions).

Endpoint: GET /api/lpr/general/get_timetable.php

Parameters: None (besides auth and output)

Response Body Fields:

Example:

curl "https://YOUR_HOST/api/lpr/general/get_timetable.php?auth=${AUTH}&output=json"

Groups

Groups allow you to manage ACL entries in batches. Each group has its own settings (barrier, email, popup, timetable, etc.) and a set of associated cameras. Plates added to a group inherit the group's settings.

List All Groups

Endpoint: GET /api/lpr/groups/list.php

Parameters: None (besides auth and output)

Response Body Fields:

Example:

curl "https://YOUR_HOST/api/lpr/groups/list.php?auth=${AUTH}&output=json"

Create Group

Endpoint: GET /api/lpr/groups/insert.php

Parameters:

Response:

{
  "error": false,
  "message": "Group ACL successfully inserted."
}

Example:

curl "https://YOUR_HOST/api/lpr/groups/insert.php?group_name=Employees&timetable_id=1&open_barrier=1&auth=${AUTH}&output=json"

Update Group

Endpoint: GET /api/lpr/groups/update.php

Parameters:

Response:

{
  "error": false,
  "message": "Group ACL successfully updated."
}

Example:

curl "https://YOUR_HOST/api/lpr/groups/update.php?group_id=5&group_name=Staff&auth=${AUTH}&output=json"

Delete Group

Endpoint: GET /api/lpr/groups/delete.php

Parameters:

Response:

{
  "error": false,
  "message": "GROUP ACL successfully deleted."
}

Example:

curl "https://YOUR_HOST/api/lpr/groups/delete.php?group_id=5&auth=${AUTH}&output=json"

List Plates in Group

Get all plate numbers assigned to a specific group.

Endpoint: GET /api/lpr/groups/list_group.php

Parameters:

Response:

{
  "error": false,
  "response": {
    "header": {
      "count": 3,
      "duration": "0.03"
    },
    "body": [
      { "plate_number": "BV01ABC" },
      { "plate_number": "BV02DEF" },
      { "plate_number": "BV03GHI" }
    ]
  }
}

Example:

AUTH=$(echo -n "5" | md5sum | awk '{print $1}')
curl "https://YOUR_HOST/api/lpr/groups/list_group.php?group_id=5&auth=${AUTH}&output=json"

Add Plate to Group (Inherit Settings)

Add a plate number to a group. The plate inherits all settings from the group (timetable, barrier, email, etc.).

Endpoint: GET /api/lpr/groups/insert_group_plate.php

Parameters:

Response:

{
  "error": false,
  "message": "Plate ACL successfully inserted.",
  "id": 42
}

Example:

AUTH=$(echo -n "BV01ABC5" | md5sum | awk '{print $1}')
curl "https://YOUR_HOST/api/lpr/groups/insert_group_plate.php?plate_number=BV01ABC&group_id=5&auth=${AUTH}&output=json"

Add Plate to Group (Custom Expiry)

Same as Add Plate to Group but allows overriding the group's expiration settings.

Endpoint: GET /api/lpr/groups/insert_group_plate_custom.php

Parameters:

Example:

EXPIRE=$(date -d '+7 days' +%s)
AUTH=$(echo -n "BV01ABC${EXPIRE}05" | md5sum | awk '{print $1}')
curl "https://YOUR_HOST/api/lpr/groups/insert_group_plate_custom.php?plate_number=BV01ABC&group_id=5&expire=${EXPIRE}&auth=${AUTH}&output=json"

Parking

The Parking module manages vehicle entry/exit tracking, parking fees, and space availability.

Cars Inside Location

Get all vehicles currently inside a parking location.

Endpoint: GET /api/lpr/parking/cars_inside.php

Parameters:

Response Body Fields:

Example:

AUTH=$(echo -n "3" | md5sum | awk '{print $1}')
curl "https://YOUR_HOST/api/lpr/parking/cars_inside.php?location_id=3&auth=${AUTH}&output=json"

Parking Events

Get a history of parking events (entries) for a location within a date range.

Endpoint: GET /api/lpr/parking/events.php

Parameters:

Response Body Fields:

Example:

curl "https://YOUR_HOST/api/lpr/parking/events.php?location_id=3&start=2025-07-15&end=2025-07-15&auth=${AUTH}&output=json"

Get Parking Price

Calculate the parking fee for a vehicle currently inside a location.

Endpoint: GET /api/lpr/parking/get_parking_price.php

Parameters:

Response Body Fields:

Example:

AUTH=$(echo -n "3BV01ABC" | md5sum | awk '{print $1}')
curl "https://YOUR_HOST/api/lpr/parking/get_parking_price.php?location_id=3&plate_number=BV01ABC&auth=${AUTH}&output=json"

Get Plate Numbers Inside

Get a simple list of plate numbers currently inside a location. Optionally filter by partial plate match.

Endpoint: GET /api/lpr/parking/get_plate_numbers_inside.php

Parameters:

Response:

{
  "error": false,
  "response": {
    "header": {
      "location_id": "3",
      "plate_number": "BV",
      "count": 2
    },
    "body": [
      { "number": "BV01ABC" },
      { "number": "BV02DEF" }
    ]
  }
}

Example:

curl "https://YOUR_HOST/api/lpr/parking/get_plate_numbers_inside.php?location_id=3&plate_number=BV&auth=${AUTH}&output=json"

Set Paid Amount

Record a parking payment for a vehicle. This marks the vehicle as charged and generates a receipt.

Endpoint: GET /api/lpr/parking/set_paid_amount.php

Parameters:

Response:

{
  "error": false,
  "response": {
    "header": {
      "location_id": "3",
      "plate_number": "BV01ABC",
      "count": 1
    },
    "body": [
      {
        "number": "BV01ABC",
        "price": 15.00,
        "status": "OK"
      }
    ]
  }
}

Example:

AUTH=$(echo -n "3BV01ABC15.001parking_fee" | md5sum | awk '{print $1}')
curl "https://YOUR_HOST/api/lpr/parking/set_paid_amount.php?location_id=3&plate_number=BV01ABC&value=15.00&cash_register=1&receipt_item_id=parking_fee&payment_method=card&auth=${AUTH}&output=json"

Parking Spaces by Tenant

Get parking space allocation and occupancy per tenant at a location.

Endpoint: GET /api/lpr/parking/spaces.php

Parameters:

Response Body Fields:

Example:

curl "https://YOUR_HOST/api/lpr/parking/spaces.php?location_id=3&auth=${AUTH}&output=json"

Parking Statistics

Get total parking capacity and current occupancy for a location.

Endpoint: GET /api/lpr/parking/stats.php

Parameters:

Response:

{
  "error": false,
  "response": {
    "header": {
      "location_id": "3",
      "duration": "0.02"
    },
    "body": [
      {
        "parking_spaces": 100,
        "cars_inside": 67,
        "free_spaces": 33
      }
    ]
  }
}

Example:

curl "https://YOUR_HOST/api/lpr/parking/stats.php?location_id=3&auth=${AUTH}&output=json"

Tenant Cars

Get all vehicles inside a location that belong to a specific tenant.

Endpoint: GET /api/lpr/parking/tenant.php

Parameters:

Response Body Fields:

Example:

AUTH=$(echo -n "31" | md5sum | awk '{print $1}')
curl "https://YOUR_HOST/api/lpr/parking/tenant.php?location_id=3&tenant_id=1&auth=${AUTH}&output=json"

Event Confirmation

Confirm or cancel a parking event. This is typically called by the parking payment kiosk or mobile app after the driver has confirmed their exit.

Endpoint: GET /api/lpr/parking/event_confirmation.php

Parameters:

Response:

• "OK" — Event processed successfully
• "Error" — Invalid request

Example:

curl "https://YOUR_HOST/api/lpr/parking/event_confirmation.php?id=1&number=BV01ABC&type=no"

Error Handling

All endpoints return a consistent error structure:

JSON Errors

{
  "error": true
}

Or with a descriptive message:

{
  "error": true,
  "message": "Description of the error."
}

Common Error Messages

Webhooks / Callbacks

Groups can be configured with an action_url that receives a callback when a plate from that group is detected. The URL supports the following placeholder:

Example:

action_url = "https://your-app.com/webhook/lpr?plate=#PLATE_NUMBER&camera=#CAMERA_ID"

When plate BV01ABC is detected on camera 3, the system calls:

https://your-app.com/webhook/lpr?plate=BV01ABC&camera=3

Complete Integration Checklist

To integrate with Metrici LPR, follow these steps:

1. Obtain API Key — Get your api_key from the Metrici LPR admin panel.
2. Discover Resources — Use general/get_locations.php and general/get_cameras.php to find your location and camera IDs.
3. Query Detections — Use list.php or search.php to retrieve plate detection history.
4. Manage Access — Use insert_action.php or groups to add authorized plates.
5. Set Up Webhooks — Configure action_url on groups for real-time detection notifications.
6. Handle Parking — Use the parking endpoints to track vehicles, calculate fees, and process payments.
7. Clean Up — Schedule delete_expired.php to periodically remove expired ACL entries.

Notes

• All date parameters accept YYYY-MM-DD format or any format compatible with PHP's strtotime().
• Timestamp parameters (expire, expiration_beginning) are Unix timestamps (seconds since epoch).
• The output parameter is case-sensitive: use json, xml, or dump.
• Query parameters are case-insensitive (the API normalizes them to lowercase internally).
• The API uses HTTP GET for all endpoints.
• The base URL path is /api/lpr/ relative to your Metrici LPR installation.