What is  syntax in PHP code?
Reference — What does this symbol mean in PHP?
Converting truth tables to boolean expressions I have start learning Selenium WebDriver, but i am confused between Java and Python. Which language should i choose? I do have basic ideas of Core Java but haven't wrote a single piece of code with python.  So please suggest me which is the better language for Selenium WebDriver? What are the differences between a bridge camera and a DSLR? What  are the differences between a bridge camera and a DSLR? What server control panels are available for Ubuntu Server? As a dedicated Ubuntu server or as a VPS, I am looking for a web control panel, something like cPanel which is something like a web administrator for a server.  I have not used any on Linux since I do everything through the terminal, but still want to know what I can use in the case I have to recommend Ubuntu Server with such an application installed. I've tried to setup an autologin, but that isn't possible, because my home is encrypted. What are the reasons for this?  PS. Here I have described my problem: . Diamond moderator rollbacks can resurrect blacklisted tags Does "+" use in String concatenation affect efficiency? Order Bars in ggplot2 bar graph I had recently faced a problem:     Solve the Diophantine Equation $x^2 - y! = 2001$.   Solving it was quite easy. You show how $\forall y \ge 6$, $9|y!$ and since $3$ divides the RHS, it must divide the LHS and if $3|x^2 \implies 9|x^2$ and so the LHS is divisible by $9$ and the RHS is not. Contradiction. Hence, the only solution is $(45, 4)$.  That made me wonder, how we can solve the Diophantine Equation $x^2 - y! = 2016$. We cannot apply the same logic here. $2016$ is a multiple of $9$ and it is clear that $3|x$ and $9 \nmid x$. How do I proceed from here? Radiation– white vs black house, hot or cool? In my book's thermodynamics chapter, it says that an      "object that radiates heat faster also absorbs heat faster. This means   that an object that is a more efficient radiator comes to equilibrium   with its environment more quickly. With this in mind, is it better to   paint your house black or white?"   I am confused which it would be. The book says white because      "in summer, you house is cooler than the environment and white   reflects away the heat. In winter your house is warmer than the   environment and white radiates away the heat" Why less temperature at high altitude Why there is always cold at high altitudes. e.g. at peak of mountains. Also as we go high from sea level, temperature starts decreasing. Why is it? Regex exec only returning first match How to skip kernel update? xdg-open on debian 9 fails to open browser I decided to try lxdm (was using fluxbox and xfce), and discovered that for many programs the url handler was failing, producing this error message;   Quite strange as you can see, it's prepending the user directory to the url.  The example here is from telegram, but it happens in discord, as well as when executing from the command line; xdg-open https://www.google.com produces a similar error. xdg-settings get default-web-browser output's firefox.desktop which works as a link in both xfce and lxdm.  More information; I ran bash -x on it and...  $ bash -x /usr/bin/xdg-open http://www.google.com + check_common_commands http://www.google.com + '[' 1 -gt 0 ']' + parm=http://www.google.com + shift + case "$parm" in + '[' 0 -gt 0 ']' + '[' -z '' ']' + unset XDG_UTILS_DEBUG_LEVEL + '[' 0 -lt 1 ']' + xdg_redirect_output=' &gt; /dev/null 2&gt; /dev/null' + '[' xhttp://www.google.com '!=' x ']' + url= + '[' 1 -gt 0 ']' + parm=http://www.google.com + shift + case "$parm" in + '[' -n '' ']' + url=http://www.google.com + '[' 0 -gt 0 ']' + '[' -z http://www.google.com ']' + detectDE + unset GREP_OPTIONS + '[' -n LXDE ']' + case "${XDG_CURRENT_DESKTOP}" in + DE=lxde + '[' xlxde = x ']' + '[' xlxde = x ']' + '[' xlxde = x ']' + '[' xlxde = xgnome ']' + '[' -f /run/user/1000/flatpak-info ']' + '[' xlxde = x ']' + DEBUG 2 'Selected DE lxde' + '[' -z '' ']' + return 0 + case "${BROWSER}" in + case "$DE" in + open_lxde http://www.google.com + pcmanfm --help -a is_file_url_or_path http://www.google.com ++ file_url_to_path http://www.google.com ++ local file=http://www.google.com ++ echo http://www.google.com ++ grep -q '^file:///' ++ echo http://www.google.com + local file=http://www.google.com + echo http://www.google.com + grep -q '^/' ++ pwd + file=/home/nesmerrill/.local/share/applications/http://www.google.com + pcmanfm /home/nesmerrill/.local/share/applications/http://www.google.com + '[' 0 -eq 0 ']' + exit_success + '[' 0 -gt 0 ']' + exit 0   The important part seems to be pcmanfm --help -a is_file_url_or_path http://www.google.com but, that command if that's how it was used, doesn't seem to do much of anything?  $ pcmanfm --help -a is_file_url_or_path http://www.google.com Usage:   pcmanfm [OPTION…] [FILE1, FILE2,...]    Help Options:   -h, --help                   Show help options   --help-all                   Show all help options   --help-gtk                   Show GTK+ Options  Application Options:   -p, --profile=PROFILE        Name of configuration profile   -d, --daemon-mode            Run PCManFM as a daemon   --no-desktop                 No function. Just to be compatible with nautilus   --desktop                    Launch desktop manager   --desktop-off                Turn off desktop manager if it's running   --desktop-pref               Open desktop preference dialog   --one-screen                 Use --desktop option only for one screen   -w, --set-wallpaper=FILE     Set desktop wallpaper from image FILE   --wallpaper-mode=MODE        Set mode of desktop wallpaper. MODE=(color|stretch|fit|crop|center|tile|screen)   --show-pref=N                Open Preferences dialog on the page N   -n, --new-win                Open new window   -f, --find-files             Open a Find Files window   --role=ROLE                  Window role for usage by window manager   --display=DISPLAY            X display to use Apparently this is a  and should hopefully be fixed in an upcoming update.    I have installed SQL Server Management Studio v17.9 on a clean Windows 10 installation.  This associated all .sql files with SSMS.  I want to associate .sql files with a plain text editor (eg: Sublime) but I am unable to change the default application.  I have tried:   Right click .sql file -> Open With -> Sublime + "Always use this program". Settings -> Default Applications by File Type -> Find .sql -> Change to Sublime Right click .sql file -> Properties -> "Change" button -> Sublime. Using ftype via elevated command prompt as seen    In all 3 cases, my selection is not reflected in any way, anywhere.  The icon remains SSMS, and the file opens with SSMS.  Is there some kind of "File Association retention" setting within SSMS I am unaware of?  Edit: I can change the default application for non-SSMS-associated extensions without issue.  Edit: after deleting registry key HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.sql, .sql files show a VSCode icon:    If I then double-click New Users.sql, it opens with SSMS and a refresh of regedit shows the .sql entry recreated with ssms.exe associated (the icon remains VSCode):    If I then right-click -> open with -> Choose Another App -> Select Sublime and hit "Always use this to open .sql files", it opens with Sublime and a refresh of regedit shows a new "b" entry created for Sublime.  The icon remains VSCode, and double-clicking opens it in SSMS:    If I then delete the a entry for ssms.exe and rename b -> a such that only sublime exists, then double-click the .sql file, it opens with SSMS and generates a new b entry for itself: I am developing a set of scripts, which I want to be present for all users, when I set up a server. But I don't want them in the standard locations like /usr[/local]/[bin],[sbin] etc.  Is there some existing convention for where such scripts should be placed? The command history between sessions is not getting saved. I'm using guake and the history for the session is working fine. I noticed that .bash_history had some commands I executed in sudo -s mode and tried the same again and all the commands while in the session got saved so I tried: chmod 777 .bash_history  Now the old commands appear at the start of a session but no new commands are getting saved. Why does US Robotics destroy Lanning's house? Shortly after the death of Dr. Lanning, Detective Spooner travels to the doctor's house to look for clues.  While he is searching the house a demolition bot (which had been programmed to demolish the house the next day) goes on a rampage and destroys the house with Detective Spooner in it.   The house is fully furnished and appears to be in good condition. Why would US Robotics want to destroy the house with everything in it? Why not sell the house and everything inside? Why use gradient descent with neural networks? When training a neural network using the back-propagation algorithm, the gradient descent method is used to determine the weight updates. My question is: Rather than using gradient descent method to slowly locate the minimum point with respect to a certain weight, why don't we just set the derivative $\frac{d(\text{Error})}{dw}=0$, and find the value of weight $w$ which minimizes the error? Also, why are we sure that the error function in back-propagation will be a minimum? Can't it turn out the error function is a maximum instead? Is there a specific property of the squashing functions that guarantees that a network with any number of hidden nodes with arbitrary weights and input vectors will always give an error function that has some minima? How can I overwrite/print over the current line in Windows command line? On Unix, I can either use \r (carriage return) or \b (backspace) to overwrite the current line (print over text already visible) in the shell.  Can I achieve the same effect in a Windows command line from a Python script?  I tried the curses module but it doesn't seem to be available on Windows.