A class with a function inside a function

1

I know it seems kinda confusing but it really isn’t. I want to start coding using OOP.

I created a class named Form.
Form has a method to add text fields called addTextField.
Form has another method to add fieldsets called addFieldset.

I want to use the addTextField method inside the addFieldset method, since a fieldset is composed of several text fields.

Here is the code I have so far

class Form
{

	// Declare a class member variable
	var $form;

	function addFormAttributes($urlQuery)
	{
		$urlQuery = trim($urlQuery);
		if(!empty($urlQuery))
		{
			$urlQuery = '?'.$urlQuery;
		}
		$this->form .= '<form name="" action="'.$_SERVER['PHP_SELF'].$urlQuery.'" method="POST">';
	}

	// --- Operators/Methods/Functions/Actions ---
	function addTextField($label, $name, $value, $tablename, $column, $validation='')
	{
		$_POST[$name] = trim($_POST[$name]);
		if($validation == 'required')
		{
			$hint = '<em class="required">(required)</em>';
			if(isset($_POST[$name]) && $_POST['process'] == 1 && empty($_POST[$name]))
			{
				$feedback = '<span class="formFeedback">This field is required</span>';
			}
		}
		$this->form .= '<p><label for="'.$name.'">'.$label.' '.$hint.'</label><input type="text" name="'.$name.'" value="'.$value.'" />'.$feedback.'</p>';
		$feedback='';
		$hint='';
	}

	function addFieldset($legend, $fields)
	{
		$this->form .= '<fieldset><legend>'.$legend.'</legend>';
		foreach($fields as $key => $value)
		{
			if($value[0]=='text')
			{
				$this->form .= addTextField($value[1], $value[2], $value[3], $value[4], $value[5]);
			}
		}
		$this->form .= '</fieldset>';
	}

	function addSubmitButton($value)
	{
		$this->form .= '<p><input type="submit" value="'.$value.'"></p>';
	}

	// Gets the form
	function get()
	{
		$this->form = $this->form.'<input type="hidden" name="process" value="1"></form>';
		return $this->form;
	}
}

It gives me this error message: “Fatal error: Call to undefined function: addtextfield()”

What does it mean “undefined function”? I did define it.