unexpected T_ENCAPSED_AND_WHITESPACE, expecting T_STRING or T_VARIABLE or T_NUM_STRING error

try this

echo $sqlupdate1 = "UPDATE table SET commodity_quantity=$qty WHERE user='".$rows['user']."' ";

Try

$sqlupdate1 = "UPDATE table SET commodity_quantity=$qty WHERE user={$rows['user']} ";

You need curly brackets for array access in double quoted strings.

Use { before $ sign. And also add addslashes function to escape special characters.

$sqlupdate1 = "UPDATE table SET commodity_quantity=".$qty."WHERE user=".addslashes($rows['user'])."'";