PHP validation on forms - php

Question

I've five fields in the form
When a form is submitted and if three fields are not filled,it should validate and show errors on those three fields.
I used to do it using if loops,this will show one error at a time,instead, I want to show all the errors.
I want to check special characters,empty validation,min and max characters on each field.
preg_match('/^[a-z\d ]{3,20}$/i', $category
How to check them all at once using PHP?
Update
$errors = array();
$required = array("Name", "Email");
foreach($_POST as $key=>$value)
{
if(!empty($value))
{
$$key = $value;
}
else
{
if(in_array($key, $required))
{
array_push($errors, $key);
}
}
}
This can be used to check empty validation for all fiedls,how do i check for special characters,alpha numeric characters,the provblem would be each field will have different regex.
For eg: phone number and email can not have same regex.
Thanks in advance!

Answer 1

$errors = array();
if (preg_match('/^[a-z\d ]{3,20}$/i', $name)) {
$errors[] = "Please enter valid name.";
}
if (preg_match('/^[a-z\d ]{3,20}$/i', $category)) {
$errors[] = "Please enter valid category.";
}
if (preg_match('/^[a-z\d ]{3,20}$/i', $amount)) {
$errors[] = "Please enter valid amount.";
}
if(!empty($errors))
{
echo "The was an error filling out the form:<br><ul>";
foreach($errors as $msg)
{
echo "<li>$msg</li>";
}
echo "</ul>Please try again.";
}
Or, to make it more concise, use something like Ananth's answer.
// your 3 fields that need to be validated; Key is field, Value is error message if check invalid.
$validate = array("name" => "Please enter valid name.", "category" => "Please enter a real category.", "amount" => "Please enter an amount.");
$error = array();
foreach ($validate as $field => $message) {
if (preg_match('/^[a-z\d ]{3,20}$/i', $$field)) {
$error[] = $message;
}
}
if(!empty($errors))
{
echo "The was an error filling out the form:<br><ul>";
foreach($errors as $msg)
{
echo "<li>$msg</li>";
}
echo "</ul>Please try again.";
}
UPDATE
Seeing as how each check has it's on regex, the first example is easy enough to solve. As for the second example, it only requires a small change.
// your 3 fields that need to be validated;
// Key is Regex, value is array with the variable name (without the $) as the key,
// and the error message as the value.
$validate = array(
'/^[a-z\d ]{3,20}$/i' => array("name" => "Please enter valid name."),
'/^[a-z\d ]{3,20}$/i' => array("category" => "Please enter a real category."),
'/^[a-z\d ]{3,20}$/i' => array("amount" => "Please enter an amount.")
);
$error = array(); // Empty array to store errors in.
foreach ($validate as $regex => $data) { // Key = $regex, Value = array($variable, $error)
if (preg_match($regex, ${$data[0]})) { // This code is untested, so try it without the braces around $data[0]
$error[] = $data[1]; // If the data matches the regular expression provided, add the provided error message to the $error array.
}
}
if(!empty($errors)) // If the $errors array isn't empty (has an error in it)
{
echo "The was an error filling out the form:<br><ul>";
foreach($errors as $msg) // Goes through each error, printing it to an unordered list.
{
echo "<li>$msg</li>";
}
echo "</ul>Please try again.";
}
Note than in the above example, each has the same example regex, but it's simple enough to change those to your needs.
EDIT
All the code above is untested, though it should work, if it doesn't, try removing the braces around $data[0], as mentioned in the accompanying comments.
UPDATE 2
If you need to add an optional checker, the same code can be modified slightly, with an extra foreach loop, for all the optional fields to check.
// your 3 fields that need to be validated;
// Key is Regex, value is array with the variable name (without the $) as the key,
// and the error message as the value.
$required = array(
'/^[a-z\d ]{3,20}$/i' => array("name" => "Please enter valid name."),
'/^[a-z\d ]{3,20}$/i' => array("category" => "Please enter a real category."),
'/^[a-z\d ]{3,20}$/i' => array("amount" => "Please enter an amount.")
);
$optional = array(
'/^[a-z\d ]{3,20}$/i' => array("shipping" => "Please enter valid shipping location."),
'/^[a-z\d ]{3,20}$/i' => array("options" => "Please enter an clean option.")
);
$error = array(); // Empty array to store errors in.
foreach ($required as $regex => $data) { // Key = $regex, Value = array($variable, $error)
if (preg_match($regex, $$data[0])) { // This code is untested, so try it with or without the braces around $data[0]
$error[] = $data[1]; // If the data matches the regular expression provided, add the provided error message to the $error array.
}
}
foreach($optional as $regex => $data)
{
if(strlen(trim($$data[0])) > 0) // If the trimmed length of the string (all leading and trailing whitespace removed) == 0?
{
if (preg_match($regex, $$data[0])) { // This code is untested, so try it with or without the braces around $data[0]
$error[] = $data[1]; // If the data matches the regular expression provided, add the provided error message to the $error array.
}
}
if(!empty($errors)) // If the $errors array isn't empty (has an error in it)
{
echo "The was an error filling out the form:<br><ul>";
foreach($errors as $msg) // Goes through each error, printing it to an unordered list.
{
echo "<li>$msg</li>";
}
echo "</ul>Please try again.";
}

Answer 2

$validate = array("name", "category", "amount"); // your 3 fields that need to be validated
$error = '';
foreach ($validate as $field) {
if (preg_match('/^[a-z\d ]{3,20}$/i', $$field)) {
$error .= $field;
}
}
Later, based on $error you can show your errors.