Fonction Catch that image pour lien extérieur

FUNCTION.PHP

<form id="thumbnail_upload" method="post" action="">
<label>Titre</label>
<input type="text" name="title" id = "title" style = "width:70%" required></br><br/>
	<input type = "hidden" name = "save" value = 1>
<div class = "thumbnailform">
	<div class == "thumbinput" style = "width:75%;float:left">

FONCTION CATCH THAT IMAGE ?

	</div>
	<div class = "thumbpreview" id = "thumbprev" style = "width:20%;float:right"></div>
</div>
<div style = "clear:both"></div>
</br>
<label>URL </label>
<input type="url" name="content" value="http://" placeholder="http://" />



PLUGIN.PHP

<?php if ( has_post_thumbnail() ) { ?>
				<div class = 'reddit-image pull-left' style = 'width:180px'>
					<img src = "<?php echo $image[0]; ?>" width = "180px" class="img-rounded">
				</div>