PDO BindParam不会每次都在while循环上绑定

Question

我通过PHP中的PDO连接到SQL Server数据库.我的问题是为什么每次while循环运行时都不能将参数绑定到命名的位置标记？这是代码:

    public function search($search, $field)
{
    $c = new PDO("sqlsrv:Server=localhost;Database=$this->_db", $this->_user, $this->_pass);

    $sql = "
    SELECT Title 
    FROM Table WHERE 1=1"; 
    //form array of search terms stored in serachArray variable
    $searchArray = explode(' ', $search );
    //count objects in array
    $num_search_terms = count( $searchArray );
    $i = 0;//for search term array (starts at 0)
    $x = 1;//for parameter incrementin (starts at 1)
    while( $i <= ( $num_search_terms -1 ) )
    {
        $sql .= "
        AND $field LIKE :s".$x;
        $stmt = $c->prepare( $sql );

        $currTerm = "%" . $searchArray[ $i ] . "%";

        $stmt->bindParam( ':s'.$x, $currTerm );         

        $i++;
        $x++;
    }

    $stmt->execute();

    while ( $row = $stmt->fetch( PDO::FETCH_OBJ ) )
    {
       print $row->Title;
    }
}

结果集返回空,没有错误.肯定应该从此搜索返回数据.当我只输入一个搜索词时,它工作正常.但是,当我输入多个时,我总是得不到任何结果.

Answer 1

您正在准备循环内的每个不完整的查询片段.您应该只准备一次,并且应该准备完整的 SQL查询.

更新:不确定您在哪里查找文档,但bindParam()手册页有几个示例:

<?php
/* Execute a prepared statement by binding PHP variables */
$calories = 150;
$colour = 'red';
$sth = $dbh->prepare('SELECT name, colour, calories
    FROM fruit
    WHERE calories < :calories AND colour = :colour');
$sth->bindParam(':calories', $calories, PDO::PARAM_INT);
$sth->bindParam(':colour', $colour, PDO::PARAM_STR, 12);
$sth->execute();
?>

如果你在循环中这样做,你将不会得到任何有用的东西:

$stmt->bindParam( ':s'.$x, $currTerm );  

...但您之前删除并创建了一个新$stmt对象.