Random Password Generator



The code used for index.php is below:

<!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">
    <link rel="stylesheet" href="../styles.css">
    <title>Random Password Generator</title>
</head>
<body>
    <?php

        $error = '';

        if(isset($_POST['generate'])){
            $charset = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789%$#@!&()*-+^?><{}[]|";
            $washed_chars = htmlentities($charset);
            $password_length = htmlentities($_POST['password-length']);
            $length_limit = 25;

            if(!$password_length){
                $err = "<h2>Password Length is Required</h2>";
                $error = $err;
            } 
            else if($password_length > $length_limit){
                $err = "<h2>Password Must Be 25 Characters or Less</h2>";
                $error = $err;
            } 
            else {
                $generated_password = substr(str_shuffle($washed_chars), 0, $password_length);
            }
        }

        echo "<h1 class='lesson-h1'>Random Password Generator</h1>";
    ?>
    <form action="index.php" method="post">
        <textarea name="user-password" id="user-password" placeholder="Password Generates Here" cols="30">
            <?php 
                if(isset($generated_password)){echo $generated_password;}
            ?>
        </textarea>
        <br>
        <label for="password-range">Desired Password Length: 
        <br>
        <input type="number" name="password-length" id="password-length" maxlength="2" placeholder="Choose: 1-25 Characters">
        </label>
        <br>
        <input type="submit" value="Generate" name="generate">
    </form>
    <h3><?php echo $error; ?></h3>
    <hr>
    <?php
        include('../show_code.php');
        show_code('index.php');
    ?>

</body>
</html>