php - fatal error : Call to a member function prepare() on a non-object

Question

我们有一个文档管理应用程序。我在 mysql DB 中加载了 5000 个图像文件。在客户端删除文件夹时需要将其删除。

使用以下代码，

public function delete($dbh){

    $sql = "DELETE FROM fileTable WHERE FID=:fid;
            DELETE FROM file_blobTable WHERE FID=:fid";
    $stmt = $dbh -> prepare($sql);
    $stmt -> bindParam(":fid", $this->fid, PDO::PARAM_INT);
    $this -> fdid = -1; //
    if ($stmt -> execute()) {
        return 0;
    }
    return 1;
}

上面的函数就是这样循环调用的，

// Loop through the folder and delete all the files it contains.

foreach ($files as $fileID) {
     // Get DB handle
     $dbh1 = DB::getWriteDB();

      $f = new File($fileID);
      $f -> delete($dbh1);
}

如果数据库中的图像数量少于 500，那么当我们删除时，这将非常有效。 如果更多，我就会遇到可怕的事情，

"Fatal error: Call to a member function prepare() on a non-object".

Answer 1

为每次调用函数删除生成准备好的语句不仅效率低下，而且很可能是导致错误的原因。您只需要准备一次查询，这是它们存在的两个主要原因之一。您可以使用静态变量:

public function delete($dbh) {
    static $sql = "DELETE FROM fileTable WHERE FID=:fid;
        DELETE FROM file_blobTable WHERE FID=:fid";
    static $stmt = $dbh -> prepare($sql);

或者，因为您无论如何都在使用对象，所以使用类变量:

static protected function getDeleteQuery($dbh) {
    static $sql = "DELETE FROM fileTable WHERE FID=:fid;
        DELETE FROM file_blobTable WHERE FID=:fid";
    if (is_null(self::$queries['delete'])) {
        self::$queries['delete'] = $dbh->prepare($sql);
    }
    return self::$queries['delete'];
}
public function delete($dbh) {
    $stmt = self::getDeleteQuery($dbh);
    ...