IF HTML element display is none, then do something, ELSE do something else - PHP

[Quekspele]

I want to make an \[code\]if\[/code\] that will do things, only if div's display is not none. Here is an example:\[code\]<div id="div_1" style="display:none;">blah blah blah</div><?php if (div_1 display is none){...} else {echo $variable;} ?>\[/code\]Any idea how will I syntax this part \[code\](div_1 display is none)\[/code\]??? If it can be of-course! Thank you in advance!