Grade Calculator

I need to do this exercise:

Create a function workOutGradeAv - this method will read in some grades, then work out and display the average grade.

Display a meaningful introductory message.

1.1 Declare any variables you need later in the code.
1.2 Display a message asking for 5 grades in 5 separate input boxes on a HTML form. You should also explain that they should input one grade per line
1.3 It should not be possible to submit the form unless all 5 fields are entered correctly and in values that are within the grade boundary
1.4 Use a do loop(to control program flow) that:
1.4.1 reads the grade from the input form into a variable.
1.4.2 (Using a logical operator) a conditional statement (If) to check if the grade is outside the range 0 to 101 (use Boolean OR) and print error message if that is true.
1.4.3 else if the grade is not 101, then add the grade to your total. end the do loop and check the grade is not 101
1.5 Calculate the average grade and display the result with a suitable message.

My code is this:

Assess1Grades.php

<!doctype html>
<html>
    <head>
        <title>Grade Assessor</title>
    </head>

    <body>
        <h2>Grade Assessor<h2>
        <table border="1">
            <tr>
                <td>
                    <table>
                        <form action="grades.php" method="post">
                            <tr>
                                <td>
                                    Enter 5 grades. One per each line:
                                </td>
                            </tr>
                            <tr>
                                <td>
                                    Grade 1: <input type="number" name="grade1" required>
                                </td>
                            </tr>
                            <tr>
                                <td>
                                    Grade 2: <input type="number" name="grade2" required>
                                </td>
                            </tr>
                            <tr>
                                <td>
                                    Grade 3: <input type="number" name="grade3" required>
                                </td>
                            </tr>
                            <tr>
                                <td>
                                    Grade 4: <input type="number" name="grade4" required>
                                </td>
                            </tr>
                            <tr>
                                <td>
                                    Grade 5: <input type="number" name="grade5" required>
                                </td>
                            </tr>
                            <tr>
                                <td align="center">
                                    <input type="submit">
                                </td>
                            </tr>
                        </form>
                    </table>
                </td>
            </tr>
        </table>
    </body>
</html>

grades.php

<!doctype html>
<html>

    <head>
        <title>Grade Assessor</title>
    </head>

    <body>
        <h2>Grade Assessor<h2>
        <table border="1">
            <tr>
                <td>
                    <table>
                        <tr>
                            <td>
                                The Average grade is:
                            </td>
                            <td>
                                <?php
                                function workOutGradeAv() {
                                    $averagegrade=$grades/5;
                                    echo "$averagegrade";
                                }
                                $grades=0;
                                do {
                                    if ($_Post["grade1"] < 0 or $_Post["grade1"] > 101) {
                                        echo "Error! Check Input.";
                                    } elseif ($_Post["grade2"] < 0 or $_Post["grade2"] > 101) {
                                        echo "Error! Check Input.";
                                    } elseif ($_Post["grade3"] < 0 or $_Post["grade3"] >101)  {
                                        echo "Error! Check Input.";
                                    } elseif ($_Post["grade4"] < 0 or $_Post["grade4"] >101)  {
                                        echo "Error! Check Input.";
                                    } elseif ($_Post["grade5"] < 0 or  $_Post["grade5"]>101 ) {
                                        echo "Error! Check Input.";
                                    } else {
                                        $grades = $grades + $_Post["grade1"] + $_Post["grade2"] + $_Post["grade3"] + $_Post["grade4"] + $_Post["grade5"];
                                    }
                                }
                                while ($_Post["grade1"]!= 101);
                                workOutGradeAv();
                                ?>
                            </td>
                        </tr>
                    </table>
                </td>
            </tr>
        </table>
    </body>
</html>

When I submit the form the output is just The Average Grade is and there is no result. What am I doing wrong?

Solution

You have multiple errors in grades.php

1)Remove unnecessary do while loop

2)replace $_Post to $_POST.PHP is case sensitive language.

3)to display grade in function you have to declare grades as global. Or pass it as parameter.

<!doctype html>
<html>

<head>
<title>Grade Assessor</title>
</head>

<body>
<h2>Grade Assessor<h2>
<table border="1">
<tr>
<td>
<table>
<tr>
<td>
The Average grade is:
</td>
<td>
<?php

function workOutGradeAv($grades) {

$averagegrade=$grades/5;
echo "$averagegrade";
}
$grades=0;

if ($_POST["grade1"] < 0 || $_POST["grade1"] > 101)   {
echo "Error! Check Input.";
} elseif ($_POST["grade2"] < 0 or $_POST["grade2"] > 101) {
echo "Error! Check Input.";
} elseif ($_POST["grade3"] < 0 or $_POST["grade3"] >101)  {
echo "Error! Check Input.";
} elseif ($_POST["grade4"] < 0 or $_POST["grade4"] >101)  {
echo "Error! Check Input.";
} elseif ($_POST["grade5"] < 0 or  $_POST["grade5"]>101 ) {
echo "Error! Check Input.";
} else {
$grades = $grades + $_POST["grade1"] + $_POST["grade2"] + $_POST["grade3"] + $_POST["grade4"] + $_POST["grade5"];
} 

workOutGradeAv($grades);
?>
</td>
</tr>
</table>
</td>
</tr>
</table>
</body>
</html>