In what situations might a PHP framework like Codeigniter handle $_POST data differently than a standard PHP script, leading to issues with data transmission?

When using a PHP framework like Codeigniter, the framework may have its own methods for handling $_POST data, which can differ from standard PHP scripts. This can lead to issues with data transmission if the $_POST data is not properly sanitized or validated according to the framework's conventions. To solve this issue, it is important to follow the framework's guidelines for handling form data and input validation.

// Example of handling $_POST data in Codeigniter
$this->load->library('form_validation');
$this->form_validation->set_rules('username', 'Username', 'required');
$this->form_validation->set_rules('password', 'Password', 'required');

if ($this->form_validation->run() == FALSE) {
    // Handle validation errors
} else {
    $username = $this->input->post('username');
    $password = $this->input->post('password');
    
    // Process the form data
}