Hi,
Can you upload a test case?
And what version are you using?
Version information
Version: 39.0.2256.48 - Opera is up to date
Update stream: Stable
System: Arch Linux (x86_64; Deepin)
I'm not sure what do you mean by test cast, but here is an example of a simple php file in my local server.
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
</head>
<body>
<form action="" method="post">
<input type="text" name="name" value="">
<input type="submit" name="name" value="Submit">
</form>
</body>
</html>
When I open it in the browser and press tab to move to the submit button the page crashes!!!