Question

因此，我需要将输入数字的最大值设置为数据库中剩余的数量。是否有可能或有一些方法来做到这一点，因为如果输入值等于或小于剩余的库存，并且如果大于它将提示输入必须小于或等于最大值。

这里是我的代码：

<?php  
    include('config.php'); 
    $resulta = mysql_query("SELECT * FROM inventory WHERE id = '$id'"); 

    while($row = mysql_fetch_array($resulta)) 
    { 
    echo 'Stock Left: ' . $row['qtyleft']; 
    } 

    $stockstring = $row['qtyleft']; 

    //$row['qty'] > = $_post['input_value']; 

    echo '<label style="color:#000000;">Qty:'; 
    echo '<input type="number" min="1" max="'.$row['qtyleft'].'" id="qty" name="qty" required = "required" /><br>'; 
?> 

Answer 1

你需要这一切进入while循环

$resulta = mysql_query("SELECT * FROM inventory WHERE id = '$id'"); 
while($row = mysql_fetch_array($resulta)){ 
    echo 'Stock Left: ' . $row['qtyleft']; 
    echo '<label style="color:#000000;">Qty:'; 
    echo '<input type="number" min="1" max="'.$row['qtyleft'].'" id="qty" name="qty" required = "required" /><br>'; 
} 

Answer 2

max函数表获得最大id：

$getMaxID=mysql_query("SELECT max(qtyleft) FROM inventory WHERE id = '$id'"); 
$row = mysql_fetch_array($getMaxID); 
$Maxno=$row['max(qtyleft)']; 

echo $Maxno; 
echo '<label style="color:#000000;">Qty:'; 
echo '<input type="number" min="1" max="'.$Maxno.'" id="qty" name="qty" required = "required" /><br>';