我还是要硬着头皮看英文版的PHP文档，虽然阅读速度比中文慢了很多，但这是一个适应的过程。

PDO — The PDO class

PDO::beginTransaction — Initiates a transaction
PDO::commit — Commits a transaction
PDO::__construct — Creates a PDO instance representing a connection to a database
PDO::errorCode — Fetch the SQLSTATE associated with the last operation on the database handle
PDO::errorInfo — Fetch extended error information associated with the last operation on the database handle
PDO::exec — Execute an SQL statement and return the number of affected rows
PDO::getAttribute — Retrieve a database connection attribute
PDO::getAvailableDrivers — Return an array of available PDO drivers
PDO::inTransaction — Checks if inside a transaction
PDO::lastInsertId — Returns the ID of the last inserted row or sequence value
PDO::prepare — Prepares a statement for execution and returns a statement object
PDO::query — Executes an SQL statement, returning a result set as a PDOStatement object
PDO::quote — Quotes a string for use in a query.
PDO::rollBack — Rolls back a transaction
PDO::setAttribute — Set an attribute
PDOStatement — The PDOStatement class

PDOStatement::bindColumn — Bind a column to a PHP variable
PDOStatement::bindParam — Binds a parameter to the specified variable name
PDOStatement::bindValue — Binds a value to a parameter
PDOStatement::closeCursor — Closes the cursor, enabling the statement to be executed again.
PDOStatement::columnCount — Returns the number of columns in the result set
PDOStatement::debugDumpParams — Dump an SQL prepared command
PDOStatement::errorCode — Fetch the SQLSTATE associated with the last operation on the statement handle
PDOStatement::errorInfo — Fetch extended error information associated with the last operation on the statement handle
PDOStatement::execute — Executes a prepared statement
PDOStatement::fetch — Fetches the next row from a result set
PDOStatement::fetchAll — Returns an array containing all of the result set rows
PDOStatement::fetchColumn — Returns a single column from the next row of a result set
PDOStatement::fetchObject — Fetches the next row and returns it as an object.
PDOStatement::getAttribute — Retrieve a statement attribute
PDOStatement::getColumnMeta — Returns metadata for a column in a result set
PDOStatement::nextRowset — Advances to the next rowset in a multi-rowset statement handle
PDOStatement::rowCount — Returns the number of rows affected by the last SQL statement
PDOStatement::setAttribute — Set a statement attribute
PDOStatement::setFetchMode — Set the default fetch mode for this statement

exec的用法：
$sql = "INSERT INTO `timetest` VALUES (null, NOW())";
$num = $dbh->exec($sql);
echo "影响了{$num}行。";

输出：影响了1行。

$sql = "INSERT INTO `timetest` VALUES (null, NOW())";
$successful = $dbh->exec($sql);
if ($successful) {
    echo "插入记录成功";
}

回复：54楼
这段代码如果改写成mysql原来的代码，就很复杂，除了执行mysql_query($sql),还需要执行mysql_affected_rows()
因为对于插入、删除、修改的SQL语句，mysql_query始终返回true

PDO::query() returns a PDOStatement object, or FALSE on failure.
query主要用于SELECT语句，返回PDOStatement对象

$content = join(", ", PDO::getAvailableDrivers());
if (!empty($content)) {
    $sql = "INSERT INTO Contents (Content, TimeCreated) VALUES (:content, NOW())";
    $stmt = $dbh->prepare($sql);
    $stmt->bindParam(":content", $content);
    $successful = $stmt->execute();
    if ($successful) {
        $num = $stmt->rowCount();
        echo "插入了{$num}条记录。";
    } else {
        echo "插入记录失败！";
    }
} else {
    echo "没有内容";
}

$content = join(", ", PDO::getAvailableDrivers());
if (!empty($content)) {
    $sql = "SELECT * FROM Contents WHERE Content = ?";
    $stmt = $dbh->prepare($sql);
    $stmt->execute(array($content));
    if ($stmt->rowCount()){
        echo "数据表中已经有相同的内容了。";
    } else {
        $sql = "INSERT INTO Contents (Content, TimeCreated) VALUES (:content, NOW())";
        $stmt = $dbh->prepare($sql);
        $stmt->bindParam(":content", $content);
        $successful = $stmt->execute();
        if ($successful) {
            $num = $stmt->rowCount();
            echo "插入了{$num}条记录。";
        } else {
            echo "插入记录失败！";
        }
    }
} else {
    echo "没有内容";
}

bindValue的用法
$sql = "SELECT * FROM Contents WHERE Content = ?";
    $stmt = $dbh->prepare($sql);
    $stmt->bindValue(1, $content);
    $stmt->execute();

对于$stmt->queryString这个属性，输出内容如下：
INSERT INTO Contents (Content, TimeCreated) VALUES (:content, NOW())
也就是语句中仍然没有包含具体的值。

if ($successful) {
            $num = $stmt->rowCount();
            echo "插入了{$num}条记录。<br>";
            echo $stmt->queryString;
        } else {
            echo "插入记录失败！";
        }