# PHP Filters

Validating data = Determine if the data is in the proper form.
Sanitizing data = Remove any illegal character from the data.

PHP filters are used to validate and sanitize external input.

---

## 1. The `filter_var()` Function
The `filter_var()` function both validates and sanitizes data. It takes two arguments: the variable you want to check, and the type of check to use.

## 2. Validating Data
Validation filters are used to validate user input.

*   `FILTER_VALIDATE_EMAIL`: Checks if the variable is a valid email address.
*   `FILTER_VALIDATE_INT`: Checks if the variable is an integer.
*   `FILTER_VALIDATE_IP`: Checks if the variable is a valid IP address.
*   `FILTER_VALIDATE_URL`: Checks if the variable is a valid URL.

```php
$email = "john.doe@example.com";

if (filter_var($email, FILTER_VALIDATE_EMAIL)) {
  echo "$email is a valid email address";
} else {
  echo "$email is NOT a valid email address";
}
```

## 3. Sanitizing Data
Sanitization filters are used to allow or remove specified characters.

*   `FILTER_SANITIZE_EMAIL`: Removes all illegal characters from an email address.
*   `FILTER_SANITIZE_URL`: Removes all illegal characters from a URL.

```php
$email = "john(.doe)@exa//mple.com";

// Remove all illegal characters from email
$email = filter_var($email, FILTER_SANITIZE_EMAIL);

echo $email; // Outputs: john.doe@example.com
```

## 4. Filter Input
The `filter_input()` function gets an external variable (e.g. from form input) and optionally filters it.

```php
// Check if "email" is sent via GET and is valid
if (!filter_input(INPUT_GET, "email", FILTER_VALIDATE_EMAIL)) {
  echo "Email is not valid";
} else {
  echo "Email is valid";
}
```

[[programming/php/php]] [[programming/php/php-forms]]