Простой php в widget WordPress

Я пытаюсь вычислить с помощью простой математики, но я не могу получить следующую форму, сделать вычисления и вывести результаты. К сожалению, я новичок. Что не так?

<?php add_action( 'wp_dashboard_setup', 'register_my_dashboard_widget' ); function register_my_dashboard_widget() { wp_add_dashboard_widget( 'net_profit_widget', 'Net Profit Calculator', 'net_profit_widget_display' ); } function net_profit_widget_display() { $subrice = $_POST['subrice']; $subnumb = $_POST['subnumb']; $payperc = "2.9"; $paystan = "0.3"; $netprof = "N/A"; $expense = "N/A"; if (!$subrice="" || !$subnumb="") { die("Please fill in all the required information!"); //exit(); } else { if(isset($_POST['submit'])) { $expense = $_POST[subrice] * (($payperc / 100) + $paystan); $netprof = ($_POST[subprice] - $expense) * $_POST[subnumb]; } } ?> <div style="color: #777;">Paypal fee per transaction: 2.9% + $0.3</div><br> <form class="netcalc" method="POST" action=""> <label for="sub-price">Subscription Price($)</label><input id="sub-price" type="text" value="<?php $_POST['subrice']; ?>"> <br><label for="total-subs">Subscriptions Sold</label><input id="total-subs" type="text" value="<?php $_POST['subname']; ?>" > <br><br><div><span class="expenses-label">Expenses</span><span class="expenses-output">$<?php echo $expense; ?></span></div> <div><span class="net-profit-label">Net Profit</span><span class="net-profit-output">$<?php echo $netprof; ?></span></div> <br><br><input id="submit" class="button button-primary" type="submit" value="Calculate"></input> </form> <?php } 

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 add_action( 'wp_dashboard_setup', 'register_my_dashboard_widget' ); function register_my_dashboard_widget() { wp_add_dashboard_widget( 'net_profit_widget', 'Net Profit Calculator', 'net_profit_widget_display' ); } function net_profit_widget_display() { $subPrice = 0; $subnumb = 0; if (array_key_exists('subprice', $_POST) !== false) { $subPrice = $_POST['subprice']; } if (array_key_exists('subnumb', $_POST) !== false) { $subnumb = $_POST['subnumb']; } $payperc = "2.9"; $paystan = "0.3"; $netprof = "N/A"; $expense = "N/A"; if ($_SERVER['REQUEST_METHOD'] == 'POST') { if ($subPrice === false || $subnumb === false ) { die("Please fill in all the required information!"); } else { $expense = $subPrice * (($payperc / 100) + $paystan); $netprof = ($subPrice - $expense) * $subnumb; } } ?> <div style="color: #777;">Paypal fee per transaction: 2.9% + $0.3</div><br> <form class="netcalc" method="POST" action="#"> <label for="sub-price">Subscription Price($)</label><input name="subprice" id="sub-price" type="text" value="<?php echo $subPrice; ?>"> <br><label for="total-subs">Subscriptions Sold</label><input name="subnumb" id="total-subs" type="text" value="<?php echo $subnumb; ?>" > <br><br><div><span class="expenses-label">Expenses</span><span class="expenses-output">$<?php echo $expense; ?></span></div> <div><span class="net-profit-label">Net Profit</span><span class="net-profit-output">$<?php echo $netprof; ?></span></div> <br><br><input id="submit" class="button button-primary" type="submit" value="Calculate"></input> </form> <?php }