This Steamapi using www.steamwebapi.com and you need a Free API Key from there.
Get a list of all inventory information from a SteamId without Steam Blocks.
Get a list of all inventory information from a SteamId blocking and calculate the total price of the inventory.
Get a list of all profile information without Steam Blocks.
Get a list of all Steamids from a ID string.
composer require steamwebapi/php-steam-api
$steamWebApi = new SteamWebApi('YOUR API KEY');
// Get Inventory
$steamWebApi->getInventory('STEAMID');
// Get Inventory And Worth
$steamWebApi->getInventoryWorth('STEAMID');
// Get Profile (Username or Url --- OR --- SteamId) -- choice one of them, only one is required, if you dont have username just send null
$steamWebApi->getProfile('Username or Url', 'SteamId');
// Convert SteamId
$steamWebApi->getSteamId('STEAMID');
If you want to add new functions, just create a pull request.