如果输入数据，PHP和MySQL检查数据库问题

Question

我在想如何检查是否没有标签输入到特定帖子的数据库中，如果没有，显示no tags have been entered。我如何使用PHP来做到这一点？

这是我的PHP & MySQL代码。

$tag = array(); 
$dbc = mysqli_query($mysqli, "SELECT tags.tag 
        FROM posts_tags 
        INNER JOIN tags ON tags.id = posts_tags.tag_id 
        WHERE posts_tags.post_id = '" . $post_id . "' 
        GROUP BY tags.tag"); 

if (!$dbc) { 
    print mysqli_error($mysqli); 
} else { 
    while($row = mysqli_fetch_array($dbc)){ 
    $tag[] = $row['tag']; 
    } 
} 

Answer 1

如果标签数组为空，则没有标签：

if(empty($tag)){ 
    echo 'no tags have been entered'; 
} 

你也可以检查的行数返回：

if(mysqli_num_rows($dbc) == 0){ 
    echo 'no tags have been entered.'; 
} 

Answer 2

使用mysqli_num_rows和这样的代码这个：

$tag = array(); 
$dbc = mysqli_query($mysqli, "SELECT tags.tag 
        FROM posts_tags 
        INNER JOIN tags ON tags.id = posts_tags.tag_id 
        WHERE posts_tags.post_id = '" . $post_id . "' 
        GROUP BY tags.tag"); 

if (!$dbc) 
{ 
    print mysqli_error($mysqli); 
} 
elseif(!mysqli_num_rows($dbc)) 
{ 
    echo "no tags have been entered"; 
} 
else 
{ 
    while($row = mysqli_fetch_array($dbc)) 
    { 
     $tag[] = $row['tag']; 
    } 
    print_r($tag); 
} 

Answer 3

$（“。signup_name_name_image”）。hide（）;

var error_signup_name = false; 

$(".signup_name").blur(function(){ 
    check_signup_name(); 
}); 

function check_signup_name() { 
    var signup_name = $.trim($('.signup_name').val()); 
    if (signup_name == '' || signup_name.length < 6 || signup_name.length > 50) { 
     $(".signup_name").css({"border":"1px solid #ff0000"}); 
     $(".signup_name_image").show(); 
     $(".signup_name_show").html("&#8226; Write Full Name in 6 to 50 alphabets"); 
     **$(".signup_name").focus();** 
     error_signup_name = true; 
    } else if (/^[a-zA-Z0-9- ]*$/.test(signup_name) == false){ 
     $(".signup_name").css({"border":"1px solid #ff0000"}); 
     $(".signup_name_image").show(); 
     $(".signup_name_show").html("&#8226; Contain invalid character"); 
     **$(".signup_name").focus();** 
     error_signup_name = true; 
    }else { 
     $(".signup_name").css({"border":"1px solid #21cc00"}); 
     $(".signup_name_image").hide(); 
    } 
} 

$("#signup_form").submit(function(){ 

    error_signup_name = false; 

    check_signup_name(); 

    if (error_signup_name == false) { 
     return true; 
    } else { 
     return false; 
    } 
}); 

$(".signup_name_image").hover(function(){ 
    $(".signup_name_show").show(); 
}, function() { 
    $(".signup_name_show").hide();} 
); 

现在重点是停留在同一领域 如何关注领域提交时