如何在PHP中填充MySQL中的复选框？

Question

I'm working with three database tables:

• Students: Can be assigned zero to many special requirements
• SpecialRequirements: Names of all special requirements that can be assigned to a student
• SpecialRequirementAssignments: Includes an associated StudentID and the name of the special requirement

I'm making a page for editing student records. I want to show all the special requirements as checkboxes and check the checkboxes that have previously been assigned to the student. In other words, I want to check the boxes whose values are equal to the values in the SpecialRequirementAssignments table.

I'm getting the following error: "Warning: Invalid argument supplied for foreach()". Have tried my best to use the correct foreach syntax, etc., but it's still not working.

The relevant part of my code. Thanks in advance!

// grab the names of the special requirements
$specialRequirementNamesQuery = "SELECT DISTINCT SpecialRequirementName 
    FROM SpecialRequirements ORDER BY SpecialRequirementName;" ;
$specialRequirementNames = mysql_query($specialRequirementNamesQuery)
    or die(mysql_error());

// grab the names of the special requirements that are selected for this student
$selectedSpecialRequirementsQuery = "SELECT SpecialRequirementName
    FROM SpecialRequirementAssignments
    WHERE StudentID = " . $StudentID . ";" ;
$selectedSpecialRequirements = mysql_query($selectedSpecialRequirementsQuery)
    or die(mysql_error());
$checkedBoxes = mysql_fetch_array($selectedSpecialRequirements);

// create the checkboxes
while ($row = mysql_fetch_array($specialRequirementNames)) {
    echo "<input type='checkbox' name='SpecialRequirementName[]' value='" 
        . $row['SpecialRequirementName'] . "' ";

    // if the SpecialRequirementAssignment record is the same as the SpecialRequirementName record, check the box
    foreach ($checkedBoxes as $value) {
        if($value==$row['SpecialRequirementName']) {
            echo "checked";
        }
    }

        echo " /> " . $row['SpecialRequirementName'] . "<br>";
}

Answer 1

Thanks to the folks who provided helpful pointers. After a short break from the project, I was able to look at it with fresh eyes, and I think I have the answer. It's working for me, anyway.

//      grab the names of the special requirements
        $specialRequirementNamesQuery = "SELECT DISTINCT SpecialRequirementName 
            FROM SpecialRequirements 
            ORDER BY SpecialRequirementName;" ;
        $specialRequirementNames = mysql_query($specialRequirementNamesQuery)
            or die(mysql_error());

//      create the checkboxes
        while ($srn = mysql_fetch_array($specialRequirementNames)) {            
            echo "<input type='checkbox' name='SpecialRequirementName[]' value='" 
                . $srn['SpecialRequirementName'] . "' ";

//          grab the names of the special requirements that are selected for this student
            $selectedSpecialRequirementsQuery = "SELECT SpecialRequirementName
                FROM SpecialRequirementAssignments
                WHERE StudentID = '" . $StudentID . "';" ;
            $selectedSpecialRequirements = mysql_query($selectedSpecialRequirementsQuery)
                or die(mysql_error());

//          compare the special requirement name to the selected special requirements
//          if they're the same, check the box
            while ($checkedBoxes = mysql_fetch_array($selectedSpecialRequirements)) {
                if(strcmp($srn['SpecialRequirementName'], $checkedBoxes['SpecialRequirementName'])==0) {
                    echo "checked";
                }
            }
            echo " /> " . $srn['SpecialRequirementName'] . "<br>";
        }