[英]Foreach inside of While Loop Looks Funny
运行此命令后,我一直得到一个奇怪的列表:
<?php
$query_Category = "SELECT * FROM blog_categories ORDER BY category ASC";
$getCategory = mysql_query($query_Category) or die(mysql_error());
?>
<div id="sheader" style="">Categories</div>
<div class="sbody" style="color:#000 !important;">
<?php
do {
?>
<div><?php echo $row_getCategory['category'];?></div>
<?php
$cat = $row_getCategory['cat_id'];
$query_Subcategory = "SELECT * FROM blog_subcategories WHERE primcat_id = '$cat' ORDER BY subcategory ASC";
$getSubCategory = mysql_query($query_Subcategory) or die(mysql_error());
$row_getSubCategory = mysql_fetch_assoc($getSubCategory);
$str = $row_getSubCategory['subcategory']; $subcategory = explode(',', $str);
foreach ($subcategory as $arraysubcat)
{
echo '<div>' . $arraysubcat . '</div>';
}
} while ($row_getCategory = mysql_fetch_assoc($getCategory));
?>
</div>
<?php mysql_free_result($getCategory); ?>
我有一个具有ID和类别的类别表,以及一个具有ID,子类别和主要类别ID的子类别表。 我运行它,它首先随机显示foreach。
我的头真的很受您的代码的伤害,但是我相信您的问题在这里:
$cat = $row_getCategory['cat_id'];
$ row_getCategory是在代码末尾获取的,因此该代码无法正常工作。
我相信你想做这样的事情
while ($row_getCategory = mysql_fetch_assoc($getCategory))
{
$cat = $row_getCategory['cat_id'];
$query_Subcategory = "SELECT * FROM blog_subcategories WHERE primcat_id = '$cat' ORDER BY subcategory ASC";
$getSubCategory = mysql_query($query_Subcategory) or die(mysql_error());
$row_getSubCategory = mysql_fetch_assoc($getSubCategory);
$str = $row_getSubCategory['subcategory'];
$subcategory = explode(',', $str);
foreach ($subcategory as $arraysubcat) {
echo '<div>' . $arraysubcat . '</div>';
}
}
}
有时在一段while
内可以进行foreach
是while
,但这不是其中之一。 首先,您正在执行do ... while
循环,这意味着无论是否找到行,您都将逐步执行所有代码,因此,如果数据库中不存在行,则可能会出现undefined index
错误。 其次,您要为外部while循环的每次迭代执行子类别查询,这意味着如果查询返回100行,那么您将发出100个查询,这不好。
最好的选择是在两个表之间创建联接,并在一个循环中逐步遍历各行,最好是while循环(与do ... while
循环相比)。
像这样:
// Made some assumptions with the query, as no schema was posted
// But should give you a starting point
$sql =
'SELECT bc.*, GROUP_CONCAT(bsc.subcategory) AS sub_categories ' .
'FROM blog_categories AS BC INNER JOIN blog_subcategories AS bsc ON bsc.primcat_id = bc.id ' .
'GROUP BY bc.id ' .
'ORDER BY bc.category ASC';
现在,只有一个查询可以检索所有类别及其关联的子类别,现在可以通过一个while循环逐步遍历它们:
$query = mysql_query($sql) or die(mysql_error());
while ($row = mysql_fetch_assoc($query)) {
<div>
<?php echo $row['category']; ?>
</div>
// To get at subcategories you can do this
$subCategories = array_map('trim', explode(',', $row['sub_categories']));
// And sort them ASC
sort($subCategories);
foreach ($subCategories as $subCategory) {
echo '<div>' . $subCategory . '</div>';
}
}
您无需为每个类别执行单独的子查询。 只需加入即可。 尝试这个:
$db = new mysqli('localhost', 'my_user', 'my_password', 'my_db');
if ($mysqli->connect_error) {
die('Connect Error (' . $mysqli->connect_errno . ') '
. $mysqli->connect_error);
}
$get_categories = $db -> query("SELECT category, subcategory
FROM blog_categories, blog_subcategories
WHERE primcat_id = cat_id
ORDER BY category ASC, subcategory ASC");
echo "<h1>Categories</h1>";
echo "<ul>";
while($row = $get_categories -> fetch_assoc()) {
echo "<li>" . $row['category'];
if($row['subcategory']) {
echo "<ul>";
foreach(explode(",",$row['subcategory']) as $subcategory ) {
echo "<li>$subcategory</li>";
}
echo "</ul>";
}
echo "</li>";
}
echo "</ul>";
我认为您不应该使用do while
从数据库中检索数据,而应该使用while
循环,因为do while
在检查条件之前运行一次循环,因此在第一个循环中,您将不会在echo $row_getCategory['category'];
获取任何数据echo $row_getCategory['category'];
变量。 因此,请尝试使用以下代码:
<?php
while ($row_getCategory = mysql_fetch_assoc($getCategory)){
?>
<div>
<?php
echo $row_getCategory['category'];
?>
</div>
<?php
$cat = $row_getCategory['cat_id'];
$query_Subcategory = "SELECT * FROM blog_subcategories WHERE primcat_id = '$cat' ORDER BY subcategory ASC";
$getSubCategory = mysql_query($query_Subcategory) or die(mysql_error());
$row_getSubCategory = mysql_fetch_assoc($getSubCategory);
$str = $row_getSubCategory['subcategory'];
$subcategory = explode(',', $str);
foreach ($subcategory as $arraysubcat) {
echo '<div>' . $arraysubcat . '</div>';
}
?>
<?php
}
?>
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