javascript - Attribute selected option into a variable to show input field using SQL -

i need attribute selected value dropdown list variable can use in sql query.

i know have use ajax or jquery can't because don't learn yet

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<!-- début php catégories -->  <?php  	$rescat=mysqli_query($conne,$reqcat);  ?>  									  <div class="form-group">    <label class="col-md-3 control-label">catégorie</label>    <div class="col-md-9">						    	<select class="form-control select" name="categorie" id="categorie" ">  	  <?php  	    while ($rowcat= mysqli_fetch_row($rescat)) {  	  ?>  	    <option value="<?php echo $rowcat[1] ?>"><?php echo $rowcat[0] ?></option>        <?php          }           $categorie = $_post['categorie'];        ?>      </select>    </div>  </div>  <!-- fin php catégories -->

thanks

for case can use form , when validate button after having selected option have recover value of option , make request