# Connecting with PHP
This guide explains how to connect a PHP application to a TimescaleDB database using the **PDO extension**. It covers setting up prerequisites, configuring the connection URI, and running a test SQL query.
### **Variables**
To connect to a TimescaleDB database, you only need **one environment variable** — the connection URI.
**Variable**
**Description**
**Purpose**
`TIMESCALE_URI`
Full TimescaleDB connection string from Elestio
Encodes all connection info in one URI
A typical URI looks like this:
```
postgresql://:@:/
```
You can find the details needed in the URI from the **Elestio service overview** details. Copy and replace the variables carefully in the URI example provided above.
[](https://docs.elest.io/uploads/images/gallery/2025-05/v6xscreenshot-2025-05-13-at-12-30-16-pm.jpg)
### **Prerequisites**
**Install PHP**
Check if PHP is installed:
```
php -v
```
If not, download and install PHP from: [https://www.php.net/downloads.php](https://www.php.net/downloads.php)
### **Code**
Once all prerequisites are set up, create a new file named `tdb.php` and add the following code and replace the `TIMESCALE_URI` with actual link or in environment setup as you wish:
```php
query("SELECT VERSION()")->fetchColumn();
echo "Connected to TimescaleDB: " . $version . PHP_EOL;
} catch (PDOException $e) {
echo "Connection failed: " . $e->getMessage() . PHP_EOL;
}
```
To execute the script, open the terminal or command prompt and navigate to the directory where `tdb.php`. Once in the correct directory, run the script with the command
```bash
export TIMESCALE_URI=postgresql://user:password@host:port/database
```
Navigate to the directory containing `tdb.php` and run:
```
php tdb.php
```
If successful, you’ll see output like: