How to use the implode function?

The implode function is not worked!

I want to show the string as follows;

id-101-102-103-104-105

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$handle = fopen($_FILES['file']['tmp_name'], "r");
while(!feof($handle)) {
	$data = fgets($handle);
	$listing = explode(",", $data);
	$id = $listing[0];
	$name=$listing[1];  // this is second column data.
	$telephone = $listing[2];
	$email = $listing[3];

	$id1 = implode("-,$id);

	echo "id = " . $id . "";

$handle = fopen($_FILES['file']['tmp_name'], “r”);<br /><br />while(!feof($handle)) {<br /><br /> $data = fgets($handle);<br /><br /> $listing = explode(“,”, $data);<br /><br /> $id = $listing[0];<br /><br /> $name=$listing[1]; // this is second column data.<br /><br /> $telephone = $listing[2];<br /><br /> $email = $listing[3];</p><br /><p> $id1 = implode(“-,$id);</p><br /><p> echo “id = ” . $id . “”;

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