SQL查询无法将新行插入表

Question

I have a chunk of PHP code that triggers if a button is pressed by the user. What I expect to happen is it checks to see if the user has the skill already assigned to them, and if not it performs an INSERT. Then if it does do nothing. And finally if the checkbox next to a skill is un-checked it checks to see if they have the skill already assigned and delete it if found.

The code is deleting the skills from the user no matter the condition of the checkboxes. Im sure I must be missing something but after starring at the code for hours I cannot see it.

Can anyone suggest a resolution?

PHP code:

if(isset($_POST['Update']))
    {

        $default = 0;

            foreach($skills_array AS $skills_id=>$skills_name)
            {
                if (isset($_POST[$skills_name]))
                {
                    if (empty($_POST[$skills_name.'exp']))
                    {
                        $exp = $default;
                    }
                    else
                    {
                        $exp = $_POST[$skills_name.'exp'];
                    }

                    $sql = $con->query("SELECT count(`UserID`) as total FROM `userskills` WHERE `UserID` = '$User' AND `SkillID` = ".$skills_id) 
                    or die(mysqli_error($con));

                    if ($row = mysqli_fetch_assoc($sql))
                    {
                        $sql = $con->query("INSERT INTO `userskills` ( `UserID`, `SkillID`, `Experience`) VALUES  ('$User', '$skills_id', '$exp')")
                        or die(mysqli_error($con));
                        //If the checkbox is not checked it will check to see if skill is already a skill assigned to the user. If they are it will delete it. If not it will ignore.   
                    }
                    else
                    {
                        $sql = $con->query("UPDATE `userskills` SET `Experience` = '$exp' WHERE `UserID` = '$User' AND `SkillID` = ".$skills_id)
                        or die(mysqli_error($con));
                    }
                } 
                else
                {
                    $sql = $con->query("DELETE FROM `userskills` WHERE `UserID` = '$User' AND `SkillID` = ".$skills_id)
                    or die(mysqli_error($con));
                }
            }

            header('Location: Account.php');
            die();
        }
        else
        {
            echo 'Incorrect password please try again.';
        }
    }

HTML Code:

<div class="RightBody">
            <form id="form2" name="form2" method="post" enctype="multipart/form-data">
                    <p><h3>Skills:</h3>
    <?php

    $result1 = $con->query("SELECT skills.`SkillID`, skills.`Description`, COUNT(userskills.`SkillID`) AS SkillUserHas, MAX(`Experience`) AS Experience
                            FROM `skills`
                            LEFT OUTER JOIN userskills
                            ON skills.`SkillID` = userskills.`SkillID` AND userskills.`UserID` = '$User'
                            GROUP BY skills.`SkillID`, skills.`Description`
                            ORDER BY FIELD(skills.`SkillID`, 1, 7, 9, 3, 4, 5, 6, 8)") 
                            or die(mysqli_error($con));



    while ($skillrow = $result1->fetch_assoc()) 
    {
    ?>
                    <div class="CheckboxText">
                    <?php
                        echo '<label>';
                        echo '<input type="checkbox" name="'.$skillrow['Description'].'" id="CheckboxGroup1_'.$skillrow['SkillID'].'" class="skillselect" value="yes" '.(($skillrow['SkillUserHas'] > 0) ? 'checked' : '').'>';
                        echo $skillrow['Description'].'</label>';
                        echo '<input type="number" name="'.$skillrow['Description'].'exp" class="expnumber" placeholder="Enter Experience in years." value="'.$skillrow['Experience'].'">';
                        echo '<br />';
                        echo '<br />';

                     } 
                     ?>
                    </div>
                    </p>
            </form>
    </div>

Answer 1

Im not familiar with PHP, but yesterday I help in a similar problem

Here you create your query but your COUNT will always return a row, and if not skill the value is 0

$sql = $con->query("SELECT count(`UserID`) as total FROM `userskills` WHERE `UserID` = '$User' AND `SkillID` = ".$skills_id) 
                    or die(mysqli_error($con));

So instead of if ($row = mysqli_fetch_assoc($sql)) you need something like

 $row = mysqli_fetch_assoc($sql);
 $skill = $row['total'];
 if ($skill == 0 )

But that doesnt solve the error you describe, delete all skills or just the one selected ?

Any way you have to check this IF that is the branch sending your skill to delete .

 if (isset($_POST[$skills_name]))

This mean your $skills_name isnt defined. Maybe you should check for the value inside the array $skills_array ?

My second guess check the code create on the webpage. Right click your page and selece see source code