Can there be 2 while loops in a single code?

[genzedu777]

Hi all,

 

Just to check if it is possible to have 2 while loops in a single code? Below are my codes.

 

 

SQL code

$tutor_id = mysqli_real_escape_string($dbc, $_GET['tutor_id']);
    $query = "SELECT tl.level_id, tl.level_name,
                     ts.subject_id, ts.subject_name, tsl.subject_level_id, 
                     IF(tosl.tutor_id='{$tutor_id}', 1, 0) as checked
              FROM tutor_level AS tl
              INNER JOIN tutor_subject_level AS tsl
                  USING (level_id)
              INNER JOIN tutor_subject AS ts
                  USING (subject_id)
              LEFT JOIN tutor_overall_level_subject AS tosl
                  ON tosl.subject_level_id = tsl.subject_level_id
                  AND tosl.tutor_id = '{$tutor_id}'
              ORDER BY tl.level_id, ts.subject_name";
    $sql = mysqli_query($dbc, $query) or die(mysqli_error($dbc));

$query1 = "SELECT tl.level_id, tl.level_name,
                     IF(tslvl.tutor_id='{$tutor_id}', 1, 0) as checked
              FROM tutor_level AS tl
              LEFT JOIN tutor_selected_level AS tslvl
                  ON tslvl.level_id = tl.level_id
                  AND tslvl.tutor_id='{$tutor_id}'
              ORDER BY tl.level_id, tl.level_name";
    $sql1 = mysqli_query($dbc, $query1) or die(mysqli_error($dbc));

PHP code (2 while loops)

//Process the results
    $checkboxes = ''; //Create variable for output
    $current_level_id = false; //Flag to check when records change level
   while($data = mysqli_fetch_array($sql)) //Iterate throug the DB results
    {
        if($current_level_id != $data1['level_id']) //Determine if this level is different from the last
        {
		print_r ($data);
            $checkboxes .= createLevelCheckboxes($subject_data, $level_data, 5);
            $current_level_id = $data['level_id'];
            $subject_data = array();
        }
        //Add the current record to the $level_data array
        $subject_data[] = $data;
    }
//$checkboxes .= createLevelCheckboxes($subject_data, $level_data, 5);

while($data1 = mysqli_fetch_array($sql1))
{
		print_r ($data1);
		$checkboxes .= createLevelCheckboxes($subject_data, $level_data, 5);
            $level_data = array();
		$level_data[] = $data1;
}

    //Call the createLevelCheckboxes() function to generate the HTML for the LAST level records
    $checkboxes .= createLevelCheckboxes($subject_data, $level_data, 5);

[Psycho]

Yes, you can have 2 while loops in the same code - BUT you cannot do a 2nd while loop to fetch the results of a db query if the results have been exhausted by the first while loop unless you reset the pointer to the beginning of the db results. But, there should never be a need to run through the results of a db query twice. Do everything you need to do with the results in the first loop.

[genzedu777]

Hi mjdamato,

 

So sorry to trouble you again, didn't expect you to reply to this thread, as I didn't want to tie you down by all my questions.

 

I don't quite get you.

But, there should never be a need to run through the results of a db query twice. Do everything you need to do with the results in the first loop.

 

How can I achieve it? Since I have 2 different queries ($query & $query1)

 

while($data = mysqli_fetch_array($sql)) //Iterate throug the DB results
    {
        if($current_level_id != $data['level_id']) //Determine if this level is different from the last
        {
		print_r ($data);
            $checkboxes .= createLevelCheckboxes($subject_data, $level_data, 5);
            $current_level_id = $data['level_id'];
            $subject_data = array();
        }
        //Add the current record to the $level_data array
        $subject_data[] = $data;
    }
//$checkboxes .= createLevelCheckboxes($subject_data, $level_data, 5);

while($data1 = mysqli_fetch_array($sql1))
{
		print_r ($data1);
		$checkboxes .= createLevelCheckboxes($subject_data, $level_data, 5);
            $level_data = array();
		$level_data[] = $data1;
}

[Psycho]

At first glance I thought you were trying to process the results of the same query twice. But, the answer is still the same - you can have two while loops on a page.

[genzedu777]

Hi mjdamato,

 

Is it possible to help me out with these 2 while loops? I am still trying to figure out what had happened. I realised what is left in $subject_data = array(); is only the last value.

 

For example, in subject_data array, there should be 3 values...Eng, Math and Sci

However at the end day, subject_data array only keeps 'Sci', the other 2 subjects are missing - 'Eng', 'Math'.

 

It seems like somehow it has been overwritten.

 

I have done some troubleshooting, and realised it is only when I execute the 2nd while loop, while ($data1 = mysqli_fetch_array($sql1)), it will overwrite the values in subject_data array

 

Do I need to store the results/values in subject_data array somewhere in another variable, before executing the 2nd while loop?

 

while($data = mysqli_fetch_array($sql)) //Iterate throug the DB results
    {
        if($current_level_id != $data['level_id']) //Determine if this level is different from the last
        {
            $levelCheckboxes .= createLevelCheckboxes($subject_data, $level_data 5);
            $current_level_id = $data['level_id'];
            $subject_data = array();
        }
        //Add the current record to the $level_data array
        $subject_data[] = $data;
    }
//$checkboxes .= createLevelCheckboxes($subject_data, $level_data, 5);

while($data1 = mysqli_fetch_array($sql1))
{

		$levelCheckboxes .= createLevelCheckboxes($subject_data, $level_data, 5);
            $level_data = array();
		$level_data[] = $data1;
}

    //Call the createLevelCheckboxes() function to generate the HTML for the LAST level records
    $levelCheckboxes .= createLevelCheckboxes($subject_data, $level_data, 5);

[Psycho]

That code makes no sense. I've alredy provided code in a separate thread. This is the wrong approach to what you are trying to accomplish.