[PHP] Funny thing with variables

[Niklas Lampén]

What causes this:
 
I have a page getting variable $BackLink with string 
"http://www.domain.com/my_page.php4";.
I accidentaly wrote <?=~$BackLink?> and what I got out was 
"—‹‹ÅÐЈˆˆÑ™–‘“ž‘›š‡‹ŒÑœ’А™™š 
šŽŠšŒ‹ ™‘‹Ñ—Ë". What causes this? What does that ~ sign do 
before a variable?
 
 
Niklas Lampén