检查空结果(php,pdo,mysql)

Question

拜托,谁能告诉我这里我做错了什么？我只是从表中检索结果然后将它们添加到数组中.一切都按预期工作,直到我检查一个空的结果...

这将获得匹配,将其添加到我的数组并按预期回应结果:

$today = date('Y-m-d', strtotime('now'));

$sth = $db->prepare("SELECT id_email FROM db WHERE hardcopy = '1' AND hardcopy_date <= :today AND hardcopy_sent = '0' ORDER BY id_email ASC");

$sth->bindParam(':today',$today, PDO::PARAM_STR);

if(!$sth->execute()) {
    $db = null ;
    exit();
}

while ($row = $sth->fetch(PDO::FETCH_ASSOC)) {
    $this->id_email[] = $row['id_email'] ;
    echo $row['id_email'] ;
}

$db = null ;
return true ;

当我尝试检查空结果时,我的代码返回'empty',但不再产生匹配结果:

$today = date('Y-m-d', strtotime('now'));

$sth = $db->prepare("SELECT id_email FROM db WHERE hardcopy = '1' AND hardcopy_date <= :today AND hardcopy_sent = '0' ORDER BY id_email ASC");

$sth->bindParam(':today',$today, PDO::PARAM_STR);

if(!$sth->execute()) {
    $db = null ;
    exit();
}

if ($sth->fetchColumn()) {
    echo 'not empty';
    while ($row = $sth->fetch(PDO::FETCH_ASSOC)) {
        $this->id_email[] = $row['id_email'] ;
        echo $row['id_email'] ;
    }
    $db = null ;
    return true ;
}
echo 'empty';
$db = null ;
return false ;

一如往常,任何帮助表示赞赏.谢谢!

Answer 1

当你这样做时,你会丢掉一个结果行$sth->fetchColumn().这不是你如何检查是否有任何结果.你做

if ($sth->rowCount() > 0) {
  ... got results ...
} else {
   echo 'nothing';
}

相关文档:http://php.net/manual/en/pdostatement.rowcount.php

Answer 2

如果您可以选择使用fetchAll(),那么如果没有返回任何行,它将只是空数组.

count($sql->fetchAll(PDO::FETCH_ASSOC))

将返回返回的行数.

Answer 3

虽然这是一个老话题,但我认为我会考虑到最近我必须处理这个问题.

您不应该将rowCount用于SELECT语句,因为它不可移植.我使用isset函数来测试select语句是否有效:

$today = date('Y-m-d', strtotime('now'));

$sth = $db->prepare("SELECT id_email FROM db WHERE hardcopy = '1' AND hardcopy_date <= :today AND hardcopy_sent = '0' ORDER BY id_email ASC");

//I would usually put this all in a try/catch block, but kept it the same for continuity
if(!$sth->execute(array(':today'=>$today))) 
{
    $db = null ;
    exit();
}

$result = $sth->fetch(PDO::FETCH_OBJ)

if(!isset($result->id_email))
{
    echo "empty";
}
else
{
    echo "not empty, value is $result->id_email";
}

$db = null;

当然,这仅适用于单个结果,就像循环数据集时一样.

Answer 4

$sql = $dbh->prepare("SELECT * from member WHERE member_email = '$username' AND member_password = '$password'");

$sql->execute();

$fetch = $sql->fetch(PDO::FETCH_ASSOC);

// if not empty result
if (is_array($fetch))  {
    $_SESSION["userMember"] = $fetch["username"];
    $_SESSION["password"] = $fetch["password"];
    echo 'yes this member is registered'; 
}else {
    echo 'empty result!';
}