อยากทราบว่า เวลาแก้ไขข้อมูล จะให้ checked ใน checkbox ที่เคยเลือกไว้ยังไงครับ

if(true){echo"checked";}

<input type="checkbox" name="ccc1" <?php if($val1 == 1){ echo "checked"; } ?> value="1" />

<?	
	$sql2 = "select EVTL_Role_Admin from EVTL_Member where EVTL_Username = '$EVTL_Username'";
	mysql_query("SET NAMES UTF8");
	$Results = mysql_query($sql2);
	$Num_Rows = mysql_num_rows($Results);
	$num_Row = mysql_fetch_array($Results);
	$EVTL_Role_Admin = $num_Row['EVTL_Role_Admin'];

	$data = explode(",",$EVTL_Role_Admin);

	$sql = "select * from EVTL_Dept Order By EVTL_Dept_No";
	$dbquery = mysql_db_query(EVTL, $sql);

	$num_rows = mysql_num_rows($dbquery);

	$i=0;
	while ($i < $num_fields)
		{
			$field_name[$i] = mysql_field_name($dbquery, $i);
			echo "<Td bgcolor=skyblue>".$field_name[$i]."</Td>";
			$i++;
		}

	$i=0;
	while ($i < $num_rows)
		{
			$result				= mysql_fetch_array($dbquery);
			$EVTL_Dept_No		= $result[EVTL_Dept_No];
			$EVTL_Dept_Name		= $result[EVTL_Dept_Name];
?>
	<input type='checkbox' name='EVTL_Role_Admin[]'<? if($data[$i] == $$EVTL_Dept_No){
	echo "checked";} ?> value='<? $EVTL_Dept_No ?>'> <? echo $EVTL_Dept_Name;?> <br>
<?										$i++;
		}
?>

<?	
	$sql2 = "select EVTL_Role_Admin from EVTL_Member where EVTL_Username = '$EVTL_Username'";
	mysql_query("SET NAMES UTF8");
	$Results = mysql_query($sql2);
	$Num_Rows = mysql_num_rows($Results);
	$num_Row = mysql_fetch_array($Results);
	$EVTL_Role_Admin = $num_Row['EVTL_Role_Admin'];

	$data = explode(",",$EVTL_Role_Admin);

	$sql = "select * from EVTL_Dept Order By EVTL_Dept_No";
	$dbquery = mysql_db_query(EVTL, $sql);

	$num_rows = mysql_num_rows($dbquery);

	$i=0;
	while ($i < $num_fields)
		{
			$field_name[$i] = mysql_field_name($dbquery, $i);
			echo "<Td bgcolor=skyblue>".$field_name[$i]."</Td>";
			$i++;
		}

	$i=0;
	while ($i < $num_rows)
		{
			$result				= mysql_fetch_array($dbquery);
			$EVTL_Dept_No		= $result[EVTL_Dept_No];
			$EVTL_Dept_Name		= $result[EVTL_Dept_Name];
?>
	<input type='checkbox' name='EVTL_Role_Admin[]'<? if($data[$i] == $EVTL_Dept_No){
	echo "checked";} ?> value='<? $EVTL_Dept_No ?>'> <? echo $EVTL_Dept_Name;?> <br>
<?										$i++;
		}
?>

<input type='checkbox' name='EVTL_Role_Admin[]'<? if(in_array($EVTL_Dept_No, $data)){echo "checked";} ?> value='<? $EVTL_Dept_No ?>'>

<?php
$arr = [
	'123' => 'ทดสอบ1',
	'234' => 'ทดสอบ2',
	'345' => 'ทดสอบ3',
	'456' => 'ทดสอบ4',
];

$data = '123,456';

foreach($arr as $arrK => $arrV) {
	$newArr = explode(",", $data);
	if(in_array($arrK, $newArr)){
		$checked = "checked";
	}
	else {
		$checked = "";
	}
	echo '<input type="checkbox" name="checkbox_'.$arrK.'" value="'.$arrK.'" '.$checked.' />'.$arrV.'<br />';
}