php实现两表合并成新表并且有序排列的方法

<?php
/**
la (3,5,8,11)
lb(2,6,9,11,15)
合并为lc,有序排列.
用php实现,不能用sort之类的函数!!!!
**/
class union {
??? var $lista = array();
??? var $listb = array();
??? var $listc = array();
????
??? function getlenght($arr) { //获得表长度
??????? return count($arr);
??? }
????
??? function getelement($arr,$n) { //获取表中第n个元素,返回
??????? return $e = $arr[$n] ? $arr[$n] : '';
??? }
????
??? function listinsert($arr,$e) { //表末尾插入元素
??????? $arr[] = $e;
??????? return $arr;
??? }
}
$phpig = new union();
$lista = $phpig->lista = array(3,11);
$listb = $phpig->listb = array(2,15);
$listc = $phpig->listc;
$lena = $phpig->getlenght($lista); //取得表大小
$lenb = $phpig->getlenght($listb);
$i = $j = 0;
while($i < $lena && $j < $lenb) {
??? $ea = $phpig->getelement($lista,$i);
??? $eb = $phpig->getelement($listb,$j);
??? if($ea <= $eb) {
??????? $listc = $phpig->listinsert($listc,$ea);
??????? ++$i;
??? } else {
??????? $listc = $phpig->listinsert($listc,$eb);
??????? ++$j;
??? }
}
while($i < $lena) {
??? $ea = $phpig->getelement($lista,$i);
??? $listc = $phpig->listinsert($listc,$ea);
??? ++$i;
}
while($j < $lenb) {
??? $eb = $phpig->getelement($listb,$j);
??? $listc = $phpig->listinsert($listc,$eb);
??? ++$j;
}
print_r($listc);
?>