A simple program to ask the user to give five numbers and then the program will determine which of the five numbers has the highest, and lowest numerical value using PHP programming language.

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My email address is the following jakerpomperada@gmail.com, jakerpomperada@aol.com, and jakerpomperada@yahoo.com.My mobile number here in the Philippines is 09173084360.

Program Listing

<?php
    if(isset($_POST["btnSubmit"])) {
        $highest = max($_POST["input1"],
                    $_POST["input2"],
                    $_POST["input3"],
                    $_POST["input4"],
                    $_POST["input5"]);
        
        $lowest = min($_POST["input1"],
                    $_POST["input2"],
                    $_POST["input3"],
                    $_POST["input4"],
                    $_POST["input5"]);
    }
?>
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Highest &amp; Lowest Numbers</title>
    <style>
        *,html {
            box-sizing: border-box;
            padding: 0;
            margin: 0;
        }
        body {
            display: flex;
            justify-content: center;
            align-items: center;
            min-height: 100vh;
            background: #fefefe;
        }

        .container {
            padding: 20px;
            border-radius: 10px;
            background: #fff;
            border: #000 solid 1px;
            text-align: center;
            min-width: 300px;
        }

        h1, h2 {
            margin: 0 0 5px;
            line-height: 1;
        }
        
        input {
            display: block;
            width: 100%;
            margin-bottom: 10px;
            padding: 10px;
            font-size: 15px;
        }

        input:last-of-type {
            margin: 0;
        }

        .output_wrapper {
            padding: 20px;
            font-size: 20px;
            background-color: #ccc;
            margin: 10px 0;
            border: none;
        }

        .output {
            margin: 10px 0 0;
        }

        button,
        .btnRetry {
            background-color: #4CAF50;
            color: #fff;
            border: none;
            border-radius: 2px;
            text-align: center;
            text-transform: uppercase;
            text-decoration: none;
            cursor: pointer;
            font-size: 15px;
            padding: 10px;
            width: 100%;
            display: block;
        }
    </style>
</head>
<body>
    <?php
        if(isset($highest, $lowest)){
            echo '<div class="container">
                    <h1>Highest &amp; Lowest Numbers</h1>
                    <h2>&#187; Jake R. Pomperada, MAED-IT, MIT &#171;</h2>

                    <div class="output_wrapper">
                        <p>Your inputs are: '
                            .$_POST["input1"] . ', ',
                            $_POST["input2"] . ', ',
                            $_POST["input3"] . ', ',
                            $_POST["input4"] . ', ',
                            $_POST["input5"] .
                        '</p>
                        <h3 class="output">Highest No: '.$highest.'<br> Lowest No: '.$lowest.'</h3>
                    </div>

                    <a href="high_low.php" class="btnRetry">Retry?</a>
                </div>';
        } else {
            echo '<form action="" method="post" class="container">
                    <h1>Highest &amp; Lowest Numbers</h1>
                    <h2>&#187; Jake R. Pomperada, MAED-IT, MIT &#171;</h2>

                    <div class="output_wrapper">
                        <input type="text" name="input1" placeholder="Enter 1st number here..." required>
                        <input type="text" name="input2" placeholder="Enter 2nd number here..." required>
                        <input type="text" name="input3" placeholder="Enter 3th number here..." required>
                        <input type="text" name="input4" placeholder="Enter 4th number here..." required>
                        <input type="text" name="input5" placeholder="Enter 5th number here..." required>
                    </div>

                    <button type="submit" name="btnSubmit">Submit</button>
                </form>';
        }
    ?>
</body>
</html>