php - PDO 查询一半时间返回 False

Question

我的 PDO mysql 查询有问题

这是我的简单代码(不是真实情况，只是为了向您展示问题)

$connexion = new PDO(SQL_DSN, SQL_USERNAME, SQL_PASSWORD);
$stmt = $connexion->prepare('SELECT * from missions,platforms WHERE missions_platforms_id = exl_platforms_id AND missions_id = :mission');
$stmt->execute(array(":mission" => '1'));
$ligne = $stmt->fetch(PDO::FETCH_ASSOC);
var_dump($stmt);

$stmt = $connexion->prepare('SELECT * from missions,platforms WHERE missions_platforms_id = exl_platforms_id AND missions_id = :mission');
var_dump($stmt);
$stmt = $connexion->prepare('SELECT * from missions,platforms WHERE missions_platforms_id = exl_platforms_id AND missions_id = :mission');
var_dump($stmt);

和输出:

object(PDOStatement)[2]
 public 'queryString' => string 'SELECT * from missions,platforms WHERE missions_platforms_id = platforms_id AND missions_id = :mission' (length=122)

boolean false

object(PDOStatement)[2]
 public 'queryString' => string 'SELECT * from missions,platforms WHERE missions_platforms_id = platforms_id AND missions_id = :mission' (length=122)

为什么第二个 var_dump 返回 false ？

如果我对相同的模式执行多次，它一半的时间会返回 false...

谢谢你

Answer 1

使用 PDOStatement::closeCursor() 使用 PDOStatement::fetch() 读取结果集后尝试关闭结果集游标如:

$connexion = new PDO(SQL_DSN, SQL_USERNAME, SQL_PASSWORD);
$stmt = $connexion->prepare('SELECT * from missions,platforms WHERE missions_platforms_id = exl_platforms_id AND missions_id = :mission');
$stmt->execute(array(":mission" => '1'));
$ligne = $stmt->fetch(PDO::FETCH_ASSOC);
var_dump($stmt);
$stmt->closeCursor();

$stmt = $connexion->prepare('SELECT * from missions,platforms WHERE missions_platforms_id = exl_platforms_id AND missions_id = :mission');
var_dump($stmt);
$stmt = $connexion->prepare('SELECT * from missions,platforms WHERE missions_platforms_id = exl_platforms_id AND missions_id = :mission');
var_dump($stmt);

第一个语句是您实际从中获取结果的唯一语句。