每次点击提交按钮时.txt文件的换行符

我希望我的代码将数据保存到文本文件中。我得到了它来这样做：

Name: Geo
Address: California
Phone Number: 661212121
# of Boxes: 1
Scheduled Date: Tues

但是，每次我再次点击提交按钮并使用 HTML 中的新数据时，它只会替换文本文件中的旧数据。

Name: Paul
Address: Sweden
Phone Number: 1234
# of Boxes: 5
Scheduled Date: Wed

我想使输出看起来像：

Name: Geo
Address: California
Phone Number: 661212121
# of Boxes: 1
Scheduled Date: Tues
Name: Paul
Address: Sweden
Phone Number: 1234
# of Boxes: 5
Scheduled Date: Wed

我的网页：

     <form action='testing.php' method='GET'>
    Name: <br/>
    <input type='text' name='name'/>
    <br/>
    Address: <br/>
    <input type='text' name='address'/>
    <br/>
    Contact Number: <br/>
    <input type='text' name='phone'/>
    <br/>
    # of Boxes: <br/>
    <input type='text' name='box'/>
    <br/>
    Scheduled Date <br/>
    <input type='text' name='date'/>
    <br/>
    <input type='submit' value='SUBMIT'/>
</form>

和PHP：

<?php
$name = $_GET['name'];
$address = $_GET['address'];
$phone = $_GET['phone'];
$box = $_GET['box'];
$date = $_GET['date'];
$file_handle = fopen("pickup.txt", "w");
$file_contents = "Name:" . $name . "'r'n" . "Address:" . $address . "'r'n" . "Phone Number:" . $phone . "'r'n" . "# of Boxes:" . $box . "'r'n" . "Scheduled Date:" . $date;
fwrite($file_handle, $file_contents);
fclose($file_handle);
print "file created and written to pickups.txt";