Get "unknown account" when testing the sendTransaction function

[rhinogroup]

Testing the send transaction function on

/vendor/web3p/web3.php/examples/sendTransaction.php

require('./exampleBase.php');

$eth = $web3->eth;

echo 'Eth Send Transaction' . PHP_EOL;
$eth->accounts(function ($err, $accounts) use ($eth) {
    if ($err !== null) {
        echo 'Error: ' . $err->getMessage();
        return;
    }
    $fromAccount = $accounts[0];
    $toAccount = $accounts[1];

this works, this also proves that the addresses being used are definitely onchain and contain balances

    $eth->getBalance($fromAccount, function ($err, $balance) use($fromAccount) {
        if ($err !== null) {
            echo 'Error: ' . $err->getMessage();
            return;
        }
        echo $fromAccount . ' Balance: ' . $balance . PHP_EOL;
    });
    $eth->getBalance($toAccount, function ($err, $balance) use($toAccount) {
        if ($err !== null) {
            echo 'Error: ' . $err->getMessage();
            return;
        }
        echo $toAccount . ' Balance: ' . $balance . PHP_EOL;
    });

/end this works

// send transaction
$eth->sendTransaction([
    'from' => $fromAccount,
    'to' => $toAccount,
    'value' => '0x11'
], function ($err, $transaction) use ($eth, $fromAccount, $toAccount) {

the below triggers the error "unknown account", yet the above balance requests work as intended

    if ($err !== null) {
        echo 'Error: ' . $err->getMessage();
        return;
    }
    echo 'Tx hash: ' . $transaction . PHP_EOL;

/end error

        // get balance
        $eth->getBalance($fromAccount, function ($err, $balance) use($fromAccount) {
            if ($err !== null) {
                echo 'Error: ' . $err->getMessage();
                return;
            }
            echo $fromAccount . ' Balance: ' . $balance . PHP_EOL;
        });
        $eth->getBalance($toAccount, function ($err, $balance) use($toAccount) {
            if ($err !== null) {
                echo 'Error: ' . $err->getMessage();
                return;
            }
            echo $toAccount . ' Balance: ' . $balance . PHP_EOL;
        });
    });
});

Would appreciate any help