SQL查詢動態占位符

<?php // 在這段腳本中，PHP變量$title 和  $price 分別為書名和價格上限的頁面輸入值。   $sql = &#39;SELECT id,title,author,publisher,date,price FROM books&#39;;  if($title !==&#39;&#39;){//添加title查詢條件(LIKE)      $conditions[] = "title LIKE ? ESCAPE &#39;#&#39;";      $ph_type[] =&#39;text&#39;;      $ph_value[]= esape_wildcard($title);  }  if($price !== &#39;&#39;){//添加price上限查詢條件      $conditions[] = "price <= ?";      $ph_type[] =&#39;integer&#39;;      $ph_value[]= $price;  }  if(count($conditions) >?0){//存在where語句時  ????$sql?.=?'?WHERE?'.implode('?AND?',$conditions);  }  $stmt?=?$mdb2?-&gt;prepare($sql?,?$ph_type);//準備sql語句  $rs?=?$stmt-&gt;excute($ph_value);//執行變量綁定和查詢  ?  ?&gt;