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In my case, i have an API written in PHP which periodically checks the database. If certain condition was met, i need to send an alert message from the API to an account/node in the Ethereum blockchain network through smart contract. Any idea how can this be done? or is this even possible?

PS: I am using Apache web server with MYSQL database

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  • Something doesn't sound quite right in your description - "send message from the API to an account/node though a smart contract". First of all, I take it that by API you mean an off-chain client (implemented in PHP in your case). Now, the flow is usually that you send a message (transaction) from the off-chain client through a node to a smart contract. In order to send it, you need to use an account which holds enough ether. So in short, PHP client --> sign message with account's private key --> node --> smart contract.
    – goodvibration
    Dec 25, 2018 at 15:34
  • Or less recommended: unlock the account on the node (using the account's private key), and then, PHP client --> send message to node --> sign message and send to smart contract.
    – goodvibration
    Dec 25, 2018 at 15:36
  • But in any case, you do not use the smart contract in order to send a message to an account or a node.
    – goodvibration
    Dec 25, 2018 at 15:37
  • Oh i see, but how to implement the "PHP client--> sign message with account's private key " part? Do you have any example code?
    – Sienz Pz
    Dec 25, 2018 at 15:43
  • In Javascript (via web3.js), not in PHP.
    – goodvibration
    Dec 25, 2018 at 16:32

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You can use a client library for PHP (Such as : https://github.com/sc0Vu/web3.php ) to interact with Ethereum.

Example of calling a contract from PHP: 

$contract = new Contract('http://localhost:8545', $abi);
// estimate function gas
$contract->at($contractAddress)->estimateGas($functionName, $params, $callback);
// change function state
$contract->at($contractAddress)->send($functionName, $params, $callback);
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  • I thought ethereum-php is able to read-only?
    – Sienz Pz
    Dec 26, 2018 at 7:18
  • Yes, answer has been updated to use a different library.
    – Shamit Verma
    Dec 28, 2018 at 1:29

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