Store signature using a {data:} variable name

Hi Guys,
​
So i am using the signature widget and storing the image using the below code:
​
<?php
$data_uri = $this->data('signature');
$encoded_image = explode(",", $data_uri)[1];
$decoded_image = base64_decode($encoded_image);
file_put_contents("signature.png", $decoded_image)
?>
​
What I want to do is store the signature image with a unique name based on a data variable from the field i.e. {data:name}
​
How can I edit the above file_put_contents("signature.png", $decoded_image) to replace signature.png with a variable name?

file_put_contents($this->data('field_name', '') . ".png", $decoded_image);
​
Have a care though - what happens if two people put the same data in the field?

Thanks so so much! going to test this out now.
​
The field is a unique identifier via my API call so will always be unique to that user.
​
Thanks again! going to test now

Just want to update - working like a charm! Thank you!