PHP - Is this proper use of exceptions for error handling within classes?

Question

I've searched plenty on this topic and have gotten a lot of good (but different) results. Some of the results weren't quite related and it does seem to be a matter of preference in the end, but I'm interested in if I'm following good design principles or not.

If this is too vague of a question, feel free to delete it, but can you recommend where I post it instead?

Also, this is just an example. There are quite a few things in here I would normally do differently but for the sake of simplicity, I did it this way.

The code is long, but you should be able to just copy & paste it directly into a single new PHP file and run it in your environment; there is no setup required.

Specific questions

• Is this the correct way to use exceptions and handle them on the caller side?
• Should I even be using exceptions for this?
• Are my skeleton custom exceptions correct?

Code

You can view a copy in a separate window here. I will paste it here. Save it and run it in your environment, it should work as-is without any modifications:

Beware: long code ahead

<?php

    error_reporting ( E_ALL | E_STRICT );




    class MemberLoginException extends Exception
    {

        public function __construct ( $message = null, $code = 0, Exception $previous = null )
        {
            parent::__construct ( $message, $code, $previous );
        }

    }




    class AccountsInsertException extends Exception
    {

        public function __construct ( $message = null, $code = 0, Exception $previous = null )
        {
            parent::__construct ( $message, $code, $previous );
        }

    }




    class AccountsManager
    {

        protected $_accounts = array ();
        protected $_lcUsernames = array ();     # all usernames in lowercase for checking if username is taken



        public function __construct ( array $accounts = null )
        {
            $this->setAllAccounts ( $accounts );
        }



        public function __destruct ()
        {
            unset ( $this->_accounts, $this->_lcUsernames );
        }



        public function __toString ()
        {
            $return = '';

            if ( count ( $this->_accounts ) > 0 ) :

                $return = '<table>';
                $return .= '<tr><th>Username</th><th>Password</th></tr>';

                foreach ( $this->_accounts as $account ) :

                    $return .= 
                    '<tr>
                        <td>'. htmlentities ( $account['username'], ENT_QUOTES, 'UTF-8' ) . '</td>
                        <td>'. htmlentities ( $account['password'], ENT_QUOTES, 'UTF-8' ) . '</td>
                    </tr>';

                endforeach;

                $return .= '</table>';

                return $return;
            endif;
        }



        public function Clear ()
        {
            $this->_accounts = array ();
            $this->_lcUsernames = array ();
        }



        public function Authenticate ( Member $member )
        {
            $username = strtolower ( $member->getUsername () );

            if ( count ( $this->_accounts ) ) :

                foreach ( $this->_accounts as $account ) :

                    if ( strtolower ( $account['username'] ) == $username )
                        return ( bool ) ( $account['password'] == $member->getPassword () );

                endforeach;

            else :
                return false;
            endif;
        }



        public function getAllAccounts ()
        {
            return $this->_accounts;
        }



        public function setAllAccounts ( array $newValue = null )
        {
            if ( is_null ( $newValue ) )
                $this->_accounts = array ();
            else
                $this->_accounts = $newValue;
                $this->_lcUsernames = array ();

                foreach ( $this->_accounts as $account )
                    $this->_lcUsernames[] = strtolower ( $account['username'] );

            return $this;
        }



        public function hasAccount ( $username )
        {
            return in_array ( strtolower ( $username ), $this->_lcUsernames, false );
        }



        public function AddAccount ( $username, $password )
        {

            /*
            Faster to be redundant by storing a lowercase copy of the username for comparison

            if ( array_key_exists ( strtolower ( $username ), array_change_key_case ( $this->_accounts ) ) )
                throw new AccountsInsertException ( 'Unable to create account; account already exists.' );
            */

            if ( $this->hasAccount ( $username ) )
                throw new AccountsInsertException ( 'Unable to create account; account already exists.' );

            $this->_accounts[] = array (
                'username' => $username,
                'password' => $password,
            );

            $this->_lcUsernames[] = strtolower ( $username );
            return $this;
        }



        public function RemoveAccount ( $username )
        {
            if ( $this->hasAccount ( $username ) ) :
                unset ( $this->_accounts[$username] );
                unset ( $this->_lcUsernames [ strtolower ( $username ) ] );
            endif;

            return $this;
        }



        public function __Debug ()
        {
            echo "\r<pre>\r";
            print_r ( $this->_accounts );
            echo "\r</pre>\r\r\r<pre>\r";
            print_r ( $this->_lcUsernames );
            echo "\r</pre>\r\r";
        }

    }




    class Member
    {

        protected $_username = '';
        protected $_password = '';



        public function __construct ( $username, $password )
        {
            $this->setUsername ( $username );
            $this->setPassword ( $password );
        }



        public function getUsername ()
        {
            return $this->_username;
        }



        public function setUsername ( $newValue )
        {
            $this->_username = ( string ) $newValue;
            return $this;
        }



        public function getPassword ()
        {
            return $this->_password;
        }



        public function setPassword ( $newValue )
        {
            $this->_password = ( string ) $newValue;
            return $this;
        }

    }


    # create a new accounts manager which stores all accounts and handles authentication
    # the Member class would be responsible for setting session variables, etc. Manager just checks user/pass.
    $manager = new AccountsManager ();

?><!DOCTYPE html>
<html>
    <head>
        <meta charset="UTF-8" />

        <style>

            *
            {
                font-family: "Segoe UI", "Trebuchet MS", Tahoma, Arial, Helvetica, sans-serif;
            }

            body
            {
                margin: 4em 6em;
                line-height: 1.6em;
                font-size: smaller;
            }

            header
            {
                border-bottom: 2px solid #efefef;
                margin-bottom: 3em;
                padding-bottom: 1em;
            }

            h1, h2, h3, h4, h5, h6
            {
                font-weight: normal;
                letter-spacing: 1px;
                color: royalblue;
            }

            h5, h6
            {
                font-weight: bold;
            }

            header h1 sub, header h1 sup
            {
                font-size: small;
                color: #FF4400;
                letter-spacing: 2px;
            }

            section
            {
                border-bottom: 1px dotted #ccc;
                padding-bottom: 2em;
                margin-bottom: 3em;
            }

            table
            {
                border: 1px solid #eee;
                padding: 1em;
                border-right-width: 2px;
                border-bottom-width: 2px;
            }

            th
            {
                text-align: left;
                font-variant: small-caps;
                border-bottom: 1px dotted #ccc;
                padding-bottom: .75em;
                margin-bottom: .75em;
                letter-spacing: 1px;
                color: #FF4400;
            }

            td:hover
            {
                background-color: skyblue;
            }

            td
            {
                margin: 0;
                display: table-cell;
                padding: .5em;
            }

            pre
            {
                font-family: "Droid Sans Mono", Consolas, "Courier New", Courier, monospaced;
                border: 1px solid #E4E4E4;
                padding: 1em;
                line-height: 1em;
            }

            .error
            {
                color: red;
                border: 1px dotted #ccc;
            }

            .success
            {
                color: forestgreen;
                border: 1px dotted #e0e0e0;
            }

            .error, .success
            {
                padding: .75em;
                background-color: #FFFFCC;
                border: 1px solid #E4E4E4;
            }

        </style>

        <title>Sample Login System - Test Exceptions</title>
    </head>

    <body>

        <header>
            <h1>Simple Login System <sup>demonstrating exceptions&hellip;</sup></h1>
        </header>



        <section>
            <h2>No database required</h2>

            <p>To avoid time setting up your environment, this test simply uses a class that stores an array of accounts.
            Obviously, this isn't persistent (at this time) and it doesn't actually save anything anywhere except in the
            array during the script's lifetime. Upon the next request, the previous accounts will be erased.</p>
        </section>



        <section>
            <h2>Creating accounts...</h2>

            <?php

                $createList =
                    array (

                        array (
                            'username' => 'Daniel Elkins',
                            'password' => 'delkins[not-pass-for-anything]',
                        ),

                        array (
                            'username' => 'Jennifer Lynn',
                            'password' => 'lilJenn',
                        ),

                        array (
                            'username'=> 'Charlie Dog',
                            'password'=> 'grrrrr',
                        ),

                    );

                if ( $manager->setAllAccounts ( $createList ) instanceof AccountsManager ) : ?>

                    <p><strong>Accounts were created successfully!</strong> They should be listed in
                    a table below.</p>

                <?php

                else :

                ?>

                    <p class="error">There was an error creating your accounts...</p>

                <?php

                endif;

            ?>

        </section>


        <section>
            <h2>List of accounts</h2>

            <?php echo $manager; ?>

        </section>


        <section>
            <h2>Trying to create one that already exists...</h2>

            <?php

            try
            {
                $manager->AddAccount ( 'Daniel Elkins', 'delkins[not-pass-for-anything]'); ?>

                <p class="success">Account created successfully!</p>

                <?php

            }
            catch ( AccountsInsertException $exception )
            {
                ?>

                <p class="error"><?= $exception->getMessage (); ?></p>

                <?php

            }

            ?>

        </section>


        <section>
            <h2>Showing accounts again</h2>

            <?php echo $manager; ?>

        </section>


        <section>
            <h2>Valid login test</h2>

            <p>Logging in user `Daniel Elkins`&hellip;</p>

            <?php

            if ( $manager->Authenticate ( new Member ( 'Daniel Elkins', 'delkins[not-pass-for-anything]' ) ) ) : ?>

                <p class="success">Authentication successful!</p>

                <?php

            else :

            ?>

                <p class="error">Unable to login; invalid username or password!</p>

                <?php

            endif;

            ?>

        </section>


        <section>
            <h2><strong>Invalid</strong> login test</h2>

            <p>Logging in user `Doesnt_Exist`&hellip;</p>

            <?php

            if ( $manager->Authenticate ( new Member ( 'Doesnt_Exist', '1234' ) ) ) : ?>

                <p class="success">Authentication successful!</p>

                <?php

            else :

            ?>

                <p class="error">Unable to login; invalid username or password!</p>

                <?php

            endif;

            ?>

        </section>


        <section>
            <h2>Debug information</h2>

            <?php $manager->__Debug (); ?>

        </section>

    </body>

</html>

Answer 1

Is this the correct way to use exceptions and handle them on the caller side?

Seems like a reasonable approach to me. You are throwing exceptions specific to the class, thus it's easy to catch or propagate them, and only the specific ones instead of having to catch everything and filter.

Should I even be using exceptions for this?

If you consider it an exceptional circumstance that an account exists, yes.

Are my skeleton custom exceptions correct?

Yes, although you could consider adding metadata into them, such as the name of the account which was being created into AccountInsertException. It may not be necessary, but if you find yourself in a situation where it would be useful, it's just something to consider.

Otherwise the code is kind of a mess in places though but I'm assuming it's partially because of the example.