SQL query dynamic placeholder

Dynamic binding example

<?php
// 在这段脚本中，PHP变量$title 和  $price 分别为书名和价格上限的页面输入值。 
$sql = &#39;SELECT id,title,author,publisher,date,price FROM books&#39;;
if($title !==&#39;&#39;){//添加title查询条件(LIKE)
    $conditions[] = "title LIKE ? ESCAPE &#39;#&#39;";
    $ph_type[] =&#39;text&#39;;
    $ph_value[]= esape_wildcard($title);
}
if($price !== &#39;&#39;){//添加price上限查询条件
    $conditions[] = "price <= ?";
    $ph_type[] =&#39;integer&#39;;
    $ph_value[]= $price;
}
if(count($conditions) > 0){//存在where语句时
    $sql .= &#39; WHERE &#39;.implode(&#39; AND &#39;,$conditions);
}
$stmt = $mdb2 ->prepare($sql , $ph_type);//准备SQL语句
$rs = $stmt->excute($ph_value);//执行变量绑定和查询
 
?>