Upload files to a form - html

Question

I have a form on my website to allow clients to submit inquiries but I need to add the option of adding files, in this case, it would be photos.
I can't find the proper solution for this. I'm new on this matter and I hope someone can help me.
Here it is the code i have about the form:
<form enctype="multipart/form-data" name="<?=$form_name?>" id="<?=$form_name?>" method="post" action="javascript:void(0);" >
<input type="hidden" name="lang" id="lang" value="<?=$_SESSION["lang"]?>" />
<input type="hidden" name="car_id" id="car_id" value="<?=$_SESSION["car_id"]?>" />
<input type="hidden" name="current_url" id="current_url" value="<?=$_SESSION["current_url"]?>" />
<!--NOME-->
<div class="form-group">
<? $input_name = $form_name."_"."name"; ?>
<label for="<?=$input_name?>"><?=NAME?>*</label>
<input type="text" class="{target:'#<?=$input_name?>_status',tagToload:{'.<?=$input_name?>':'#<?=$input_name?>_status','.script':'#<?=$result_div?>'}} form-control watermark required" name="<?=$input_name?>" value="<?=$_POST[$input_name]?>" id="<?=$input_name?>" placeholder="<?=NAME_PLACEHOLDER?>">
</div>
<!--END NOME-->
<!--EMAIL-->
<div class="form-group">
<? $input_name = $form_name."_"."email"; ?>
<label for="<?=$input_name?>"><?=EMAIL?>*</label>
<input type="email" class="{target:'#<?=$input_name?>_status',tagToload:{'.<?=$input_name?>':'#<?=$input_name?>_status','.script':'#<?=$result_div?>'}} form-control watermark required" name="<?=$input_name?>" value="<?=$_POST[$input_name]?>" id="<?=$input_name?>" placeholder="<?=EMAIL_PLACEHOLDER?>">
</div>
<!--END EMAIL-->
<!--SUBJECT-->
<div class="form-group">
<? $input_name = $form_name."_"."subject_other"; ?>
<label for="<?=$input_name?>"><?=SUBJECT?>*</label>
<input type="text" class="{target:'#<?=$input_name?>_status',tagToload:{'.<?=$input_name?>':'#<?=$input_name?>_status','.script':'#<?=$result_div?>'}} form-control watermark required" name="<?=$input_name?>" value="<?=$_SESSION['subject']?>" id="<?=$input_name?>" placeholder="<?=SUBJECT_PLACEHOLDER?>" <?=(isset($_SESSION["subject"])) ? 'readonly="readonly"' : ''?>>
</div>
<!--END SUBJECT-->
<!--MESSAGE-->
<div class="form-group" style="margin-bottom: 10px;">
<? $input_name = $form_name."_"."message"; ?>
<label for="<?=$input_name?>"><?=MESSAGE?>*</label>
<textarea class="{target:'#<?=$input_name?>_status',tagToload:{'.<?=$input_name?>':'#<?=$input_name?>_status','.script':'#<?=$result_div?>'}} form-control watermark required" name="<?=$input_name?>" id="<?=$input_name?>" placeholder="<?=MESSAGE_PLACEHOLDER?>" rows="3"></textarea>
</div>
<!--END MESSAGE-->
<span class="blue_label blue_label_block blue_label_small" style="text-align: left;">* Campos de preenchimento obrigatório.</span>
<div class="form-group pull-right" style="margin-bottom: 20px;">
<input type="reset" class="btn btn-primary" value="<?=CLEAR?>">
<a type="button" class="btn btn-default ml20" id="formSubmitLink_<?=$form_name?>" href="javascript:;"><?=SEND?></a>
</div>
<br class="clear">
<div class="resultForm" id="<?=$result_div?>"></div>

Answer 1

<div class="form-group">
<label for="photo" class="col-lg-2 control-label">Photo</label>
<div class="col-lg-10">
<input type="file" class="form-control" id="photo" placeholder="Photo">
</div>
</div>