将一个图像更改为多个图像。

I am using form inputs for change images i already done this. Actually this images show on home page as a new titles.So i have URl input fields for changing images link.I am facing problem when i submit only one link then other one is empty so that's why other image src null.Basically i want to change which image this one old.
Is there any one know how to handle is issue.

Html

<form action="" method="post">

<input type="url" name="image1"/>

<input type="url" name="image2"/>

<input type="url" name="image3" />

<input type="submit"/>

</form>

<img src="<?php echo $img1; ?>" />

<img src="<?php echo $img2; ?>" />

<img src="<?php echo $img3; ?>" />

PHP

<?php

     $img1=$_POST['image1'];

     $img2=$_POST['image2'];

     $img3=$_POST['image3'];

?>

<form action="" method="GET">
<input type="url" name="image1"/>
<input type="url" name="image2"/>
<input type="url" name="image3" />
<input type="submit"/>
</form>


<?php
echo '<img src="'.$_GET['image1'].'"/>';
echo '<img src="'.$_GET['image2'].'"/>';
echo '<img src="'.$_GET['image3'].'"/>';
?>