如何在html表单上执行计算php脚本

Question

I make a PHP script for calculation based on pricelist. My script work powerful, but the problem is: I must enter the value directly in source code. I wouldlike to offer end-user the opportunity to use my script without any code by a simply fill html form.

I have difficulty to link my php script on the form to make this calculation.

Bellow my source code:

1. FORM

    <center>
        <form action="samepage.php" method="post">
       <input type="text" name="amount" value="0"/>F
       <input name="button" type="submit" id="button" value="CALCULATE"  />         
      </form>
   
       <br>
   

2. PHP SCRIPT

   Corresponding your Amount, YOU MUST PAY:
   // How to remplace 500 value with form value?

   // THE PRICELIST PHP SCRIPT

   <?php
   if($montant <= 5000){ // If the amount are <= to 500, 200 must add
     echo $montant + 200;
   F </h2>
       </center>
   

   I need your help, Thanks in advance!

---

I have difficulty to link my php script on the form to make this calculation.

Answer 1

if the php code is on the same page then you need to do this.

<center>
        <form action="" method="POST">
            <input type="text" name="amount" placeholder="0" />F
            <input name="submit" type="submit" value="CALCULATE"/>
        </form>
    <br>
    <strong>Corresponding your Amount, YOU MUST PAY: </strong><br><h2>
        <?php 

        if (isset($_POST['submit'])){
            $montant = $_POST['amount'];
            if ($montant <= 5000) {
                echo $montant + 200;
            } else
            if ($montant <= 10000) {
                echo $montant + 400;
            } else
            if ($montant <= 15000) {
                echo $montant + 600;
            } else
            if ($montant <= 25000) {
                echo $montant + 900;
            } else
            if ($montant <= 35000) {
                echo $montant + 1100;
            } else
            if ($montant <= 50000) {
                echo $montant + 1200;
            } else
            if ($montant <= 75000) {
                echo $montant + 1700;
            } else
            if ($montant <= 100000) {
                echo $montant + 2000;
            } else
            if ($montant <= 150000) {
                echo $montant + 2200;
            } else
            if ($montant <= 200000) {
                echo $montant + 2400;
            } else
            if ($montant <= 250000) {
                echo $montant + 2900;
            } else
            if ($montant <= 300000) {
                echo $montant + 3900;
            } else
            if ($montant <= 400000) {
                echo $montant + 4900;
            } else
            if ($montant <= 200000) {
                echo $montant + 2400;
            } else
            if ($montant <= 750000) {
                echo $montant + 7400;
            } else
            if ($montant <= 1000000) {
                echo $montant + 9900;
            } else
            if ($montant <= 2000000) {
                echo $montant + 14900;
            } else
            if ($montant <= 3000000) {
                echo $montant + 19900;
            }else{

            }
        }
?>
        F</h2>
</center>