Logical OR

if (empty($user_id) || in_array($user_id, $banned_list))

Logical AND

if (file_exists($filename) && filetime($filename) > time())
{
}

Not Equal

if ($domain !== 'somedomain.com')
{
}

When return value can be boolean or an integer

Use if ($ReturnValue === false) or $ReturnValue !== false)

If with load of a return value into a variable

Ensure you enclose the assignment in brackets or it won’t work correctly

	if (($MyVariable = SomeFunction()) > -1)
	{
		//$MyVariable contains the return value
	}