String Replace Issue. Can you help me out with this?

pwp_vimeo.php

<?php

/**
 * Code block 1
 * This block doesn't work. Having "://" in there makes this not work at all.
*/
$vimeo_id = 72170966; //Example ID.
$hash = unserialize(file_get_contents("https://vimeo.com/api/v2/video/$vimeo_id.php")); //Parses JSON to get Video info

$vimeo_thumb = $hash[0]['thumbnail_small']; //this ends up being http://secure-b.vimeocdn.com/ts/153/182/15318283_100.jpg
$vimeo_thumb = str_replace( "http://", "https://", $vimeo_thumb, $temp = 1);
echo $vimeo_thumb; //out puts http://secure-b.vimeocdn.com/ts/153/182/15318283_100.jpg


/**
 * Code block 2
 * Removing the "://" adds two "s" to the output
*/
$vimeo_id = 72170966; //Example ID.
$hash = unserialize(file_get_contents("https://vimeo.com/api/v2/video/$vimeo_id.php")); //Parses JSON to get Video info

$vimeo_thumb = $hash[0]['thumbnail_small']; //this ends up being http://secure-b.vimeocdn.com/ts/153/182/15318283_100.jpg
$vimeo_thumb = str_replace( "http", "http", $vimeo_thumb, $temp = 1);
echo $vimeo_thumb; //out puts httpss://secure-b.vimeocdn.com/ts/153/182/15318283_100.jpg

I think you just need str_replace(find, replace, string) - lose that 4th input

Thanks. Didn't work though :/