Maintaining Checkbox State Across Pages

amanning1994

I am working on an a page that posts to itselft or $PHP['self']. The form displays data from a database with checkboxes along the left-hand side for a user to select one or more individuals to compare. The checkboxes are dynamically created by using name = 'istudent[]'. If there are more than say 20 records the rest of the records are paginated to $PHP['self'] with $start and $limit variables to start out at say record 20 and limit to 20 records.

For example, if a class has 30 students, first 20 will show up and the select "next" which takes you to $PHP['self'] but starting out at record 21 and going to 30. Selecting records and selecting "compare" button sends checkmarked records to a function within $PHP['self'] to display only those selected records. Problem I have goes back to the paginated display of records before the "compare" function.

How can I select records from 1-20 and then select records from 21-30 that are checked to compare. Right now can only checkmark records that display on same page. If checkmark records from multiple pages cannot pass all to the compare function. Any ideas?

bretticus

Well, one quick thought...

This is based on the assumption that I understand correctly that you want to serialize checked boxes across multiple pages before submitting to the compare function?

The problem is that checkboxes simply do not show up in the POST header when they are unchecked (i.e. a text input will show up as 'name=' at least so you can at least validate nothing was entered.)

My original thought was to store the checkbox array in the user session. However, because of the aforementioned fact, you would have no reliable way to uncheck boxes.

You'll probably have to resort to storing checks in a database table such as:

CREATE TABLE `studentchecks` (
`id` INT UNSIGNED NOT NULL , 
`sessionid` VARCHAR( 128 ) NOT NULL
`page` INT UNSIGNED NOT NULL ,
PRIMARY KEY ( `id` , `sessionid` )
)

Then you could record each check by something like...

foreach ($_POST['istudent'] as $studentid) {
	$sql = "INSERT INTO `studentchecks` ( `id` , `sessionid` , `page` )VALUES ('$studentid', '" . session_id() . "', '$pageid') ON DUPLICATE KEY `page` = `page`";
}

and right after run...

$sql = "DELETE FROM `studentchecks` WHERE `id` NOT IN (" . implode(",", $_POST['istudent']) . ") AND `sessionid` = '" . session_id() . "' AND `page` = '$pageid'";

to clean up anything you didn't check.

This is untested and just a concept that may get you started or give you additional insight.