the best approach to giving an error message when validating - php

Question

I am a new programmer and am attempting to do some validation for a basic registration form. I have built a basic registration form that sends the user back to the same page when submitted. I have also created a user class and have created some basic validation functions. However, the functions have the error messages built into them. I obviously put the functions on the top of the registration form so when there is an error the errors are posted on the registration form. However, I have no control on how the error messages look and would like to know if there is a lot better way to somehow echo the error messages from outside the class so I can use some type of css or something else for better control of how they look. I hope that makes sense. Also when there is an error the user is sent back to an empty registration form. I was trying to figure out how to keep the valid information in the text boxes and just make them redo the invalid information. Here is a basic example of a validation I have done. I know its basic but I am very new to programming
function validate_password($password)
{
$valid = TRUE;
if ($password == '')
{
echo "<p> Please enter a value for the password </p>";
$valid = FALSE;
}
elseif($_POST['pwd'] !== $_POST['pwd2'])
{
echo "The passwords do not match please try again";
$valid = FALSE;
}
return $valid;
}

Answer 1

Don't echo them right away, instead store them for later use. You mentioned this is inside a class, so you can use a class property to hold error messages.
class YourClass
{
public $error;
function validate_password($password)
{
$valid = TRUE;
if ($password == '')
{
// Set the error message
$this->error = "Please enter a value for the password";
$valid = FALSE;
}
// etc...
}
}
Later, when you need to, you can output it in the HTML:
if (!empty($yourclass->error)) {
echo "<p class='errmsg'>{$yourclass->error}</p>\n";
}
You then just need a CSS class errmsg and you can style it how you like:
.errmsg {
color: #FF0000;
font-size: 36px;
}
Now if you have that working, you can expand it further to make the $error class property into an array and push multiple messages onto it:
// In the class, initialize it as an array
$this->error = array();
// Use the [] notation to append messages to the array.
$this->error[] = "Another error message..."
$this->error[] = "And yet another error message..."
In your presentation code, use a loop to output the messages:
// Output a big stack of error messages...
foreach ($yourclass->error as $err) {
echo "<p class='errmsg'>$err</p>\n";
}

Answer 2

What I normally do with classes and their errors is have a variable specifically for the errors.
So something like:
class User
{
private $_ValidationErrors = array();
function validate_password($password)
{
$this->_ValidationErrors = array();
$valid = TRUE;
if ($password == '')
{
$this->_ValidationErrors[] = "Please enter a value for the password";
$valid = FALSE;
}
elseif($_POST['pwd'] !== $_POST['pwd2'])
{
$this->_ValidationErrors[] = "The passwords do not match please try again";
$valid = FALSE;
}
return $valid;
}
function ValidationErrors ()
{
if (count($this->_ValidationErrors) == 0)
return FALSE;
return $this->_ValidationErrors;
}
}
Then to use:
$user = new User();
if (!$user->validate_password('somepass'))
echo implode('<BR>',$user->ValidationErrors ());
EDIT: To display errors by the user something like:
<?php
if (isset($_POST["submit"]))
{
$user = new User();
$passwordErrors = (!$user->validate_password($_POST["pass1"]))?$user->ValidationErrors():array();
}
?>
<form action="<?php echo $_SERVER["php_self"]; ?>" method="post">
<input type="text" name="pass1" value="<?php echo htmlspecialchars($_POST["pass1"]); ?>" /><BR/>
<?php
echo ((isset($passwordErrors) && count($passwordErrors) == 0)?"":implode("<BR/>", $passwordErrors));
?>
<input type="submit" name="submit" value="Register" />
</form>