Checar campos requeridos

[vissiontotal]

Hola amigos ya he estado buscando como loco y no encuentro como hacer para que este codigo cheque los campos que son requeridos antes de pasar al paso número dos... al presionar SIGUIENTE....

Código:

<?php if (!defined("AT_DIR")) die('!!!'); ?>
<?php $this->add_script( 'jquery.selectik', 'assets/js/jquery/jquery.selectik.js'); ?>
<?php $this->add_script( 'jquery.form', 'assets/js/jquery/jquery.form.js'); ?>
<?php $this->add_script( 'jquery.validate', 'assets/js/jquery/jquery.validate.js'); ?>
<?php $this->add_script( 'plupload', 'assets/js/plupload/plupload.full.min.js'); ?>
<?php $this->add_script( 'vehicles', 'assets/js/vehicles.js'); ?>
<?php $this->add_script( 'google-map', 'https://maps.googleapis.com/maps/api/js?v=3.exp'); ?>
<?php $this->add_script( 'jquery.gmap3', 'assets/js/jquery/jquery.gmap3.js'); ?>
	<div class="step_breadcrumb">
		<a href="#" class="active" id="step_1"><?php echo __( 'step 1. announcement', AT_TEXTDOMAIN );?></a>
		<a href="#" class="" id="step_2"><?php echo __( 'step 2. specifications', AT_TEXTDOMAIN );?></a>
		................................
	</div>
<font color="red" size="4">Los campos con asterisco con obligatorios</font>

	<div class="sell_box step_1" style="display:;">
		<h2><?php echo __( '<strong>Vehicle</strong> data', AT_TEXTDOMAIN );?></h2>
		<div class="col_1">
			<div class="select_wrapper">
				<label><span>* </span><strong><?php echo __( 'Transport Type:', AT_TEXTDOMAIN ); ?></strong></label>
				<select class=" text" id="_transport_type_id" name="_transport_type_id" required value-invalid="0" >
					<option value="0"><?php echo __( 'Select', AT_TEXTDOMAIN ); ?></option>
					<?php foreach ($transport_types as $key => $value) { ?>
						<option <?php echo (!empty($car_info['options']['_transport_type_id']) && $car_info['options']['_transport_type_id']['id'] == $value['id']) ? 'selected="selected"' : ''; ?> value="<?php echo $value['id']; ?>"><?php echo $value['name']; ?></option>
					<?php } ?>
				</select>
			</div>
			<div class="select_wrapper">
				<label><span>* </span><strong><?php echo __( 'Make:', AT_TEXTDOMAIN ); ?></strong></label>
				<select class=" text select2" id="_manufacturer_id" name="_manufacturer_id" <?php echo ( !empty($car_info['options']['_manufacturer_id'] )  ? 'readonly' : ' required  value-invalid="0"' ); ?>>
					<option value="0"><?php echo __( 'Select', AT_TEXTDOMAIN ); ?></option>
					<?php if( !empty( $car_info['options']['_manufacturer_id'] ) ) { ?>
					<option selected="selected" value="<?php echo $car_info['options']['_manufacturer_id']['id']; ?>"><?php echo $car_info['options']['_manufacturer_id']['name']; ?></option>
					<?php } else { ?>
						<?php foreach ($manufacturers as $key => $value) { ?>
							<option <?php echo (!empty($car_info['options']['_manufacturer_id']) && $car_info['options']['_manufacturer_id']['id'] == $value['id']) ? 'selected="selected"' : ''; ?> value="<?php echo $value['id']; ?>"><?php echo $value['name']; ?></option>
						<?php } ?>
					<?php } ?>
				</select>
			</div>
			
			<div class="input_wrapper price">
				<label><span>* </span><strong><?php echo __( 'Currency:', AT_TEXTDOMAIN ); ?></strong></label>
				<select class="text" id="_currency_id" name="_currency_id">
					<?php foreach ($currencies as $key => $value) { ?>
						<option <?php echo (!empty($car_info['options']['_currency_id']) && $car_info['options']['_currency_id']['id'] == $value['id']) ? 'selected="selected"' : ''; ?> value="<?php echo $value['id']; ?>"><?php echo $value['name']; ?></option>
					<?php } ?>
				</select>
			</div>
			<div class="select_wrapper">
				<label><span> </span><strong><?php echo __( 'Technical condition:', AT_TEXTDOMAIN ); ?> </strong></label>
				<select class="text" id="_technical_condition_id" name="_technical_condition_id">
					<option value="0"><?php echo __( 'Select', AT_TEXTDOMAIN ); ?></option>
					<?php foreach ($technical_conditions as $key => $value) { ?>
						<option <?php echo (!empty($car_info['options']['_technical_condition_id']) && $car_info['options']['_technical_condition_id']['id'] == $value['id']) ? 'selected="selected"' : ''; ?> value="<?php echo $value['id']; ?>"><?php echo $value['name']; ?></option>
					<?php } ?>
				</select>
			</div>
			<!--
			<?php if( count($affiliates) > 0 ) {?>
			<div class="select_wrapper">
				<label><span> </span><strong><?php echo __( 'Affiliate:', AT_TEXTDOMAIN ); ?> </strong></label>
				<select class="text" id="_affiliate_id" name="_affiliate_id">
					<option value="0"><?php echo __( 'Default affiliate', AT_TEXTDOMAIN ); ?></option>
					<?php foreach ($affiliates as $key => $value) { ?>
						<option <?php echo (!empty($car_info['options']['_affiliate_id']) && $car_info['options']['_affiliate_id'] == $value['id']) ? 'selected="selected"' : ''; ?> value="<?php echo $value['id']; ?>"><?php echo $value['name']; ?></option>
					<?php } ?>
				</select>
			</div>
			<?php } ?>
			-->
		</div>
		<div class="clear"></div>
		<div class="col_all">
			<div class="input_wrapper fullwidth">
				<label><span> </span><strong><?php echo __( 'Description:', AT_TEXTDOMAIN ); ?> </strong></label>
				<textarea class="text" id="post_content" name="post_content"><?php echo (!empty($car_info['post_content']) ? $car_info['post_content'] : ''); ?></textarea>
			</div>
		</div>
		<div class="clear"></div>
		<h2></h2>
		<div class="checkbox_items">
			<span class="custom_chb_wrapper">
				<span class="custom_chb">
					<input name="_price_negotiable" type="checkbox" id="_price_negotiable" 
<?php if( isset($car_info) && (isset($car_info['options']) && isset($car_info['options']['_price_negotiable']) && !empty($car_info['options']['_price_negotiable']) && $car_info['options']['_price_negotiable'] == 'on' || $car_info['options']['_price_negotiable'] == '1')) { ?>checked="checked"<?php } ?>/>
					<input name="_price_negotiable" type="hidden" id="_price_negotiable" <?php if( isset($car_info) && (isset($car_info['options']) && isset($car_info['options']['_price_negotiable']) && !empty($car_info['options']['_price_negotiable']) && $car_info['options']['_price_negotiable'] == 'on' || $car_info['options']['_price_negotiable'] == '1' )) { ?>value="1"<?php }else{ ?> value="0"<?php } ?>/>
				</span>
				<label><?php echo __( 'Price Negotiable', AT_TEXTDOMAIN ); ?></label>
			</span>
			<!-- <span class="custom_chb_wrapper">
				<span class="custom_chb">
					<input type="checkbox" name="">
				</span>
				<label><?php echo __( 'Can be exchanged for real estate', AT_TEXTDOMAIN ); ?></label>
			</span>
			<span class="custom_chb_wrapper">
				<span class="custom_chb">
					<input type="checkbox" name="">
				</span>
				<label><?php echo __( 'Can be exchanged for real estate', AT_TEXTDOMAIN ); ?></label>
			</span> -->
		</div>
		<h2></h2>
		<div class="btn-next">
			<a href="#" class="btn1"><?php echo __( 'Next', AT_TEXTDOMAIN ); ?></a>
		</div>
	</div>
	<div class="sell_box step_2" style="display:none;">
		<h2><?php echo __( '<strong>Technical</strong> Specifications', AT_TEXTDOMAIN );?></h2>
		<div class="col_1">
			<div class="select_wrapper">
				<label><span> </span><strong><?php echo __( 'Transmission:', AT_TEXTDOMAIN ); ?></strong></label>
				..................................................................................

		<div id="loaded-images"></div>
		<div class="foto_wrapper" id="container">
			<span id="upload-photos">
				<img src="<?php echo AT_Common::static_url('/assets/images/upload.png');?>" alt="" class="upload"/>
				<?php echo __( 'upload photo', AT_TEXTDOMAIN );?>
			</span>
		</div>
		<div class="clear"></div>
		<h2></h2>
		<div class="btn-next">
			<a href="#" class="btn3"><?php echo __( 'Back', AT_TEXTDOMAIN );?></a>
			<?php if (empty($car_info)) { ?>
			<a href="#" class="btn1"><?php echo __( 'Add', AT_TEXTDOMAIN );?></a>
			<?php } else { ?>
			<a href="#" class="btn1"><?php echo __( 'Save', AT_TEXTDOMAIN );?></a>
			<?php } ?>
			<span class="form_loading"><img src="<?php echo AT_Common::static_url('assets/images/loading.gif'); ?>" /></span>
		</div>
	</div>
	</form>
</div>