Php 将th值设为NULL，如果为空，则不执行where

我现在：

$inhoud = $_POST['inhoud'];
if($inhoud == "") {
    echo $inhoud;
    $inhoud = NULL;
    echo $inhoud;
}

$sql = 'SELECT DISTINCT bestanden.id AS id,
               bestanden.uploader AS uploader,
               bestanden.name AS name,
               bestanden.mime AS mime,
               bestanden.size AS size,
               bestanden.created AS created,
               zoeken.open_id AS open_id,
               zoeken.woord AS woord
        FROM bestanden
        LEFT JOIN zoeken ON bestanden.id = zoeken.open_id 
        WHERE zoeken.woord = "' . $inhoud . '" AND
              bestanden.name LIKE "%' . $_POST['naam'] . '%" AND
              bestanden.mime LIKE "%' . $_POST['formaat'] . '%"
              AND bestanden.created LIKE "%' . $_POST['datum'] . '%";';
$result = mysql_query($sql);

但是当我搜索时，$inhoud是空的，我没有得到任何结果，因为那里没有空的（“”）（inhoud）空间。可以在我的mysql\u查询中使用if或其他内容吗？

使用空函数

    $sql = 'SELECT DISTINCT bestanden.id AS id, bestanden.uploader AS uploader, bestanden.name AS name, bestanden.mime AS mime, bestanden.size AS size, bestanden.created AS created, zoeken.open_id AS open_id, zoeken.woord AS woord FROM bestanden LEFT JOIN zoeken ON bestanden.id = zoeken.open_id 
    WHERE 1=1';
if(!empty($inhoud))
    $sql.=' AND zoeken.woord="' . $inhoud . '"';
$sql.=' AND bestanden.name LIKE "%' . $_POST['naam'] . '%" AND bestanden.mime LIKE "%' . $_POST['formaat'] . '%" AND bestanden.created LIKE "%' . $_POST['datum'] . '%"';
$result = mysql_query($sql);

empty($inhound);

看这里：

也许是斯特伦（）

。它们不再得到维护，并且已经开始使用。看到了吗？相反，学习，并使用，或-将帮助您决定哪一个。如果您选择PDO

您可以尝试以下方法：

$inhoud = $_POST['inhoud'];
if ($inhoud == "") {
    echo $inhoud;
    $inhoud = NULL;
    echo $inhoud;
}

$sql = 'SELECT DISTINCT bestanden.id AS id,
               bestanden.uploader AS uploader,
               bestanden.name AS name,
               bestanden.mime AS mime,
               bestanden.size AS size,
               bestanden.created AS created,
               zoeken.open_id AS open_id,
               zoeken.woord AS woord
        FROM bestanden
        LEFT JOIN zoeken ON bestanden.id = zoeken.open_id 
        WHERE ';
if(!empty($inhoud)) {
    $sql .= 'zoeken.woord = "' . $inhoud . '" AND';
}
$sql .= 'bestanden.name LIKE "%' . $_POST['naam'] . '%" AND
         bestanden.mime LIKE "%' . $_POST['formaat'] . '%"
         AND bestanden.created LIKE "%' . $_POST['datum'] . '%";';

$result = mysql_query($sql);

---

首先，您不应该假设在任何情况下都设置了

$\u POST[…]

（除非您已经检查了是否已设置）。正确的用法是：

$inhoud = null:
if( isset( $_POST['inhound'])){
    $inhound = trim( $_POST['inhound']); // Trim to prevent strings like "    "
    if( strlen( $inhound) < 1){
        $inhound = null;
    }
}

---

尝试使用mysqli而不是mysql。

$inhoud = null:
if( isset( $_POST['inhound'])){
    $inhound = trim( $_POST['inhound']); // Trim to prevent strings like "    "
    if( strlen( $inhound) < 1){
        $inhound = null;
    }
}

$sql = 'SELECT DISTINCT bestanden.id AS id, bestanden.uploader AS uploader,
            bestanden.name AS name, bestanden.mime AS mime,
            bestanden.size AS size, bestanden.created AS created,
            zoeken.open_id AS open_id, zoeken.woord AS woord
       FROM bestanden
       LEFT JOIN zoeken ON bestanden.id = zoeken.open_id 
       WHERE zoeken.woord=:inhound
           AND bestanden.name LIKE :naam
           AND bestanden.mime LIKE :formaat
           AND bestanden.created LIKE :date';

$sth = $dbh->prepare($sql, array(PDO::ATTR_CURSOR => PDO::CURSOR_FWDONLY));

$sth->bindParam(':naam', isset( $_POST['naam']) ? '%' . $_POST['naam'] . '%', '%');
$sth->bindParam(':formaat', isset( $_POST['formaat']) ? '%'.$_POST['formaat'].'%', '%');
$sth->bindParam(':naam', isset( $_POST['date']) ? '%' . $_POST['date'] . '%', '%');
$sth->bindParam(':inhound', is_null( $inhound) ? '%' . $inhound . '%', '%');

$sth->execute();
$sth->fetchAll();