- str_pad: documentation ( source)
<?php
$_POST['weekcheck']=3;
$one_and_only_sql = "SELECT week, name, date FROM lucky".(intval($_POST['weekcheck'])>0)?" WHERE week = 'Week ".str_pad(strval(intval($_POST['weekcheck'])), 2, "0", STR_PAD_LEFT)." 2014'":"";
echo $one_and_only_sql;