PHP - Form question population based on user answer-CodePudding

So I'm trying to create a fuel calculator form using PHP and HTML. For the most part, I have the form pretty fleshed out, however, I'm stuck on one thing.

So I would like to create a fuel perks option that gets input from the user. The question that I wanted to pose to the user is whether or not they purchased groceries. If the user types yes, then I wanted a different input box to appear asking the user for the amount in groceries that they spent and then calculate the fuel points based on that input. However, I can't figure out how to get the initial question of how much did they spend on groceries to appear based on their answer.

Here is what I have so far:

<form method="post" action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]);?>">
        How many miles did you drive? <input type="text" name="milesDriven" value="<?php echo $milesDriven;?>">
        <span class="error">* <?php echo $milesDrivenErr;?></span>
        <br><br>
        What is your cars miles per gallon?: 
        <input type="text" name="milesPerGallon" value="<?php echo $milesPerGallon;?>">
        <span class="error">* <?php echo $milesPerGallonErr;?></span>
        <br><br>
        Type of gas used: 
        <br><br>
        <input type="radio" name="gasType" <?php if (isset($gasType) && $gasType=="87 octane - 1.89$/gal") echo "checked";?> value="1.89">87 octane - 1.89$/global
        <br><br>
        <input type="radio" name="gasType" <?php if (isset($gasType) && $gasType=="89 octane - 1.99$/gal") echo "checked";?> value="1.99">89 octane - 1.99$/global
        <br><br>
        <input type="radio" name="gasType" <?php if (isset($gasType) && $gasType=="92 octane - 2.09$/gal") echo "checked";?> value="2.09">92 octane - 2.09$/global
        <br><br>
        <input type="text" name="groceries" 
            <?php
                if ($groceries = "yes") {
                    //code here that causes the input field to appear
                    
                }else if ($groceries = "no") {
                    //do nothing and proceed with the calculation
                }
            ?>
        <input type="submit" name="submit" value="Submit">
    </form>

Can you create form inputs inside of a PHP block? Please forgive me if this is a dumb question. I'm still a beginner who's trying to learn more about backend coding.

CodePudding user response：

Create a select tag inside the if block of yes and then calculate the amount the user has spend to purchase the groceries.

CodePudding user response：

Can you create form inputs inside of a PHP block ? yes of course, you can just simply doing it like this

<?php
  if ($groceries == "yes") {
   echo "<input type='text' name='purchasedGroceries' value='".$purchasedGroceries."'">   
  } 
?>

and calculate the fuel points when $groceries == "yes"

CodePudding user response：

Hijacking as answer as I cannot create a comment yet due to low rep. Answer by @adam should work. Just echo the html code or use javascript. U can also refer here.