php顺序线性表

seqArr = $arr;        $this->length = count($arr);    }    /*     * 返回线性表中第$index个数据元素     */    public function GetElem($index) {        if (($this->length) == 0 || $index < 0 || ($index > $this->length)) {            return "Error";        }        return $this->seqArr[$index - 1];    }    /*     * 返回线性表的长度     *       */    public function ListLength() {        return $this->length;    }    /*     * 返回给定的数据元素在线性表中的位置     */    public function LocateElem($elem) {        for ($i = 0; $i < ($this->length); $i++) {            if (($this->seqArr[$i]) == $elem) {                return $i + 1;            }        }    }    /*     * PriorElem: 返回指定元素的前一个元素     */    public function PriorElem($elem) {        for ($i = 0; $i < ($this->length); $i++) {            if (($this->seqArr[$i]) == $elem) {                if ($i == 0) {                    return "Error (is null) ";                } else {                    return $this->seqArr[$i - 1];                }            }        }    }    /*     * NextElem: 返回指定元素的后一个元素     */    public function NextElem($elem) {        for ($i = 0; $i < ($this->length); $i++) {            if (($this->seqArr[$i]) == $elem) {                return $this->seqArr[$i + 1];            }        }    }    /*     * ListInsert: 在第index的位置插入元素elem     */    public function ListInsert($index, $elem) {        if (($this->length) == 0 || $index < 0 || $index > ($this->length)) {            return "Error";        }        for ($i = $index; $i < ($this->length); $i++) {            $this->seqArr[$i + 1] = $this->seqArr[$i];        }        $this->seqArr[$index] = $elem;        $this->length = $this->length + 1;        return $this->seqArr;    }    /*     * ListDelete: 删除第index位置的元素       */    public function ListDelete($index) {        if (($this->length) == 0 || $index < 0 || $index > ($this->length - 1)) {            return "Error";        }        unset($this->seqArr[$index]);        array_values($this->seqArr);        return $this->seqArr;    }}?>