检查空结果(php，pdo，mysql) [英] Checking for empty result (php, pdo, mysql)

问题描述

请，有人可以告诉我我在做什么错吗?我只是从表中检索结果，然后将它们添加到数组中.一切都会按预期进行，直到我检查结果为空为止.

Please, can anyone tell me what I'm doing wrong here? I'm simply retrieving results from a table then adding them to an array. Everything works as expected until I check for an empty result...

这将获得匹配项，将其添加到我的数组中，并按预期回显结果:

This gets the match, adds it to my array and echoes the result as expected:

$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 ;

当我尝试检查一个空结果时，我的代码返回空"，但不再产生匹配结果:

When I try to check for an empty result, my code returns 'empty', but no longer yields the matching result:

$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 ;

一如既往，我们将不胜感激.谢谢！

As always, any help is appreciated. Thanks!

推荐答案

执行$sth->fetchColumn()时，您将丢弃结果行.那不是您检查是否有任何结果的方法.你做

You're throwing away a result row when you do $sth->fetchColumn(). That's not how you check if there's any results. you do

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

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

这篇关于检查空结果(php，pdo，mysql)的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！