<?php
if($_POST){
$baslangic_tarihi = $_POST["baslangic_tarihi"];
$bitis_tarihi = $_POST["bitis_tarihi"];
$sqlim = "SELECT * FROM siparis WHERE sip_tarihi BETWEEN  $baslangic_tarihi and $bitis_tarihi ";    
$yazdir = mysql_query($sqlim);
  }else{
?>
<form action="" method="post" class="form-inline">
    <div class="input-group">
      <input class="form-control" type="date"name="baslangic_tarihi" >
    </div>
  <div class="form-group">
    <label class="text" for="exampleInputPassword2">ve</label>
    <input type="date" class="form-control" name="bitis_tarihi">
  </div>
  <button type="button" class="btn btn-default">
  <span class="glyphicon glyphicon-search"></span> Arama yap</button>
</form>
</div>

<?php
}
  
?>