How can you tell which ones were checked? Is this on the results page? I need context. Where could I get the previously selected checkboxes? $_GET? 
Dear Ray
I made one separate post on this subject though. This is on the same result page on a form and pls see below the code
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<form name="searchForm" action="/hadith/search/filter/" method="GET" accept-charset="UTF-8">
<div class="form-row">
<div class="col-md-6 col-sm-12 my-1">
<input class="form-control" type="text" name="q" value="<?php echo ((isset($_GET["q"]))?$_GET["q"]:""); ?>" placeholder="যে শব্দ দিয়ে খুঁজতে চান..." required>
</div>
<div class="col-auto my-1">
<select name="lang" id="lang" class="custom-select mr-sm-2" required>
<option value="">-ভাষা সিলেক্ট-</option>
<option value="bn" <?php if (!(strcmp("bn", ((isset($_GET["lang"]))?$_GET["lang"]:"")))) {echo "selected=\"selected\"";} ?>>শুধু বাংলা</option>
<option value="en" <?php if (!(strcmp("en", ((isset($_GET["lang"]))?$_GET["lang"]:"")))) {echo "selected=\"selected\"";} ?>>English only</option>
<option value="ar" <?php if (!(strcmp("ar", ((isset($_GET["lang"]))?$_GET["lang"]:"")))) {echo "selected=\"selected\"";} ?>>العربية</option>
<option value="all"<?php if (!(strcmp("all", ((isset($_GET["lang"]))?$_GET["lang"]:"")))) {echo "selected=\"selected\"";} ?>>বাংলা/العربية</option>
</select>
</div>
<div class="col-auto my-1">
<div class="custom-control custom-checkbox mr-sm-2">
<input type="checkbox" class="custom-control-input" id="customControlAutosizing" name="exact" value="1" <?php if (!(strcmp(((isset($_GET["exact"]))?$_GET["exact"]:""),1))) {echo "checked=\"checked\"";} ?>>
<label class="custom-control-label" for="customControlAutosizing">হুবহু শব্দে</label>
</div>
</div>
<div class="col-auto my-1">
<script language="JavaScript">
function toggle(source) {
checkboxes = document.getElementsByName('book[]');
for(var i=0, n=checkboxes.length;i<n;i++) {
checkboxes[i].checked = source.checked;
}
}
</script>
<div class="form-check pl-3">
<input type="checkbox" onClick="toggle(this)" /><span class="text-danger"> সব বই সিলেক্ট করুন</span>
</div>
<div class="form-check">
<?php
$wa_startindex = 0;
while(!$booksList->atEnd()) {
$wa_startindex = $booksList->Index;
?>
<label class="form-check-label pl-3">
<input name="book[]" type="checkbox" class="form-check-input" value="<?php echo($booksList->getColumnVal("BookID")); ?>"><?php echo($booksList->getColumnVal("BookNameBD")); ?>
</label>
<?php
$booksList->moveNext();
}
$booksList->moveFirst(); //return RS to first record
unset($wa_startindex);
unset($wa_repeatcount);
?>
</div>
</div>
<div class="col mb-2 my-1">
<button type="submit" name="WADbSearch1" class="btn btn-dark btn-block"><i class="fas fa-search"></i> খুঁজুন</button>
</div>
</div>
</form>
