I want to validate URL in PHP but the function should accept the URL even if http:// or https:// not present in the input.  Following URL's should be acceptable:  http://example.com http://www.example.com https://example.com https://www.example.com www.example.com example.com   It should not accept ftp protocol, IP address, Port, URL path, query, or fragment.
I've been looking for a simple regex for URLs, does anybody have one handy that works well?  I didn't find one with the zend framework validation classes and have seen several implementations.
Any way to tell apart a CPU defect from a mainboard defect? What to do when OP answers his/her own question in an edit? Reference question:   Sometimes users solve their own questions, which is great. Sometimes they say they've solved it and move on, which is not so great. The above question is middle-ground: the user posted an answer to his own question, but as an edit to the question instead of as a real answer.  Should any action be taken in such a case? The obvious solution is to copy the edit into a real answer. But is this the right solution? In this case, the answer is a little hidden and there are no other answers, so it appears on the unanswered list.     Related: $f:I=[\pi,2\pi]\to \mathbb{R}^2$ be given by $f(t)=(\cos t,\sin t)$  which of the following are necessarily correct?  $1$. $\exists t_0\in I$ such that $f'(t_0)=\frac{1}{\pi}(f(2\pi)-f(\pi))$  $2$. $\nexists t_0\in I$ such that $f'(t_0)=\frac{1}{\pi}(f(2\pi)-f(\pi))$  $3$.$\exists t_0\in I$ such that $\pi||f'(t_0)||\ge ||(f(2\pi)-f(\pi)||$  $4$. $f'(t)=(-\sin t,\cos t)\forall t$  $4$ is clearly true, $1$ is true by Mean Value Theorem as $f$  satisfies all the conditions of MVT? have no idea of $2$ and $3$, Thank you for help Can you make a non-polar electrolytic capacitor out of two regular electrolytic capacitors? I am currently wondering about the famous .  Where does it come from mathematically that when you point with your thumb in the direction of the current, your curved fingers will point in the direction of the $B$-field? In other words, which mathematical operation does it come from? Probably it has to do with some vector product or Stokes theorem application, but I am not quite sure about it. How to find out why "context is incorrect"? I have been trying to write my first addon for Blender over the last couple of days. One error I came across quite often is the context is incorrect error for an operation of bpy.ops.  I learned that one can ask the poll function of an operator if the context is correct, but this does not tell why the context is correct/incorrect. What would be the best way to figure that out? Only way I could think of is to look into the code of the poll function. If that is the best way, what is the fastest way to find the appropriate piece of code? Old Budrys(?) end-of-world/alien invasion of NYC story This one, from the late 1950s or early 60s (I think), features the last girl in NYC, who drives her jeep up the stairs of the main library (with the lions). She feels bad about breaking the lock, but what's a girl to do, if she wants something to read? In summertime, she drives topless and, the author writes, her bosom dances enchantingly on the steps. She lives in the boathouse on the lake in Central Park. Mysterious insect-like aliens are eating the buildings in the City.... I didn't recognize a title in Budrys or Bester's isfdb bibliogs, so I may be wrong about the author. But not about the story details: it's a memorable one. Thanks in advance for helping ID this one! Why can't Mathematica integrate this? How can I attach a file to a question? I want to attach a code file to my question, but I am not able to find a link to do it. Is attaching files possible at all? What Application Indicators are available? This question exists because it has historical significance, but it is not considered a good, on-topic question for this site, so please do not use it as evidence that you can ask similar questions here.  While you are encouraged to help maintain its answers, please understand that "big list" questions are not generally allowed on Ask Ubuntu and will be closed per the .     I installed Ubuntu 11.04 on one of my systems and I am using the Unity interface. Unity is working quite well so far but I really miss panel applets for net speed, cpu temp, and system monitor.   These applets are useful for viewing quick info. Unlike 10.10, there is no other way to get this info onto the panel or unity launcher. There are solutions like screenlets and conky but they don't feel appropriate for a clean desktop look.  If you know one then please list out any third party indicators with links so that they can be found. How to troubleshoot unwanted white spaces smartly? What is the maximum or minimum tire width I can fit on my bicycle We often get questions on bicycles.stackexchange about fitting wider or narrower tires to bicycles. We have a large number of these with answers suiting the specific bike or style of bicycle in question, but I have been unable to find one that provides a generic answer covering off all things that need to be considered. For most bicycles, the answer is the same regardless of the specific style and sizes of tires in question.   This is intended as a canonical question that we can point closed questions to. Namespaces and Operator Overloading in C++ When authoring a library in a particular namespace, it's often convenient to provide overloaded operators for the classes in that namespace.  It seems (at least with g++) that the overloaded operators can be implemented either in the library's namespace:  namespace Lib { class A { };  A operator+(const A&amp;, const A&amp;); } // namespace Lib   or the global namespace  namespace Lib { class A { }; } // namespace Lib  Lib::A operator+(const Lib::A&amp;, const Lib::A&amp;);   From my testing, they both seem to work fine.  Is there any practical difference between these two options?  Is either approach better? Finding the limit of $(1-\cos x)/x^2$ $$\lim _{x \to 0}{1-\cos x\over x^2}={2\sin^2\left(\frac{x}{2}\right)\over x^2}={\frac{2}{x^2}\cdot {\sin^2\left(\frac{x}{2}\right)\over \left(\frac{x}{2}\right)^2}}\cdot\left(\frac{x}{2}\right)^2$$  now $$\lim_{x \to 0}{\sin^2\left(\frac{x}{2}\right)\over \left(\frac{x}{2}\right)^2}=\left({\sin\left(\frac{x}{2}\right)\over \left(\frac{x}{2}\right)}\right)^2=1^2$$  So we have $$\frac{2}{x^2}\cdot \left(\frac{x}{2}\right)^2=\frac{2}{x^2}\cdot \left(\frac{x^2}{4}\right)=\frac{1}{2}$$  Are the moves right? Why was the plan for the Purple Wedding so complicated? Spoilers for A Storm of Swords / Season 4 episode 2 "The Lion and the Rose".  At the Purple Wedding,      Littlefinger and Lady Olenna Tyrell   perform their plan of      poisoning King Joffrey.   A short summary of their plan:  Littlefinger orders Ser Dontos Hollard to give Sansa Stark a beautiful silver hairnet adorned with amethysts. At least some of the amethysts are actually strangler crystals in disguise. Ser Dontos also, still under orders of Littlefinger, urges Sansa to wear the hairnet at the wedding, which she then does. At the wedding, when Lady Olenna greets Sansa, she fusses her hairnet a bit, while secretly taking one of the strangler crystals. Later, during the wedding, Lady Olenna puts the crystal in Joffrey's royal cup, poisoning him.  But why was their plan so complicated? Why couldn't Lady Olenna just bring a strangler crystal with her to the wedding (as suggested in )?  Then they wouldn't depend on Ser Dontos and Sansa who could unknowingly have done something to prevent the success of the plan.  The only reason that I could think of, is Littlefinger and Lady Olenna plan for Sansa (and Tyrion as her husband with her) to take the blame for Joffrey's death.  They put the crystals on her person, so that upon examination it would clearly show that Sansa had the murder weapon on her. But Littlefinger had a plan he did not tell Lady Olenna, namely rescuing Sansa during the chaos ensuing the murder (and thereby leaving Tyrion behind as the only accused).  Is there anything confirming or debunking this theory? If my theory doesn't hold up, is there another explanation for why the plan was so needlessly complicated? Bravo for allowing comment editing, but what's the explanation for enforcing a five-minute window?  I think this might be over-engineering. If I have a spelling mistake or an inaccuracy I'd like to fix, I don't think the fact that five minutes has elapsed should prevent me from fixing it.  Further, if you are worried people will edit their comments in a way that makes the comment thread nonsensical, they can already do this by deleting their comment. So, limiting the ability to edit isn't really helping much in that regard.  Update  If people don't like this idea, I'm definitely open to hearing your reasons. For now, it seems like an unnecessary limitation of a quite awesome feature.  Update 2  Regarding John's scenario...     Me: Obama is cool!   You: You are right, man!      My edit: Obama is an idiot!   You: You are right, man!   ...this problem can still occur with deletions...     user1: Obama is cool!   user2: No, McCain is cool!   you: You are right, man!        user1: Obama is cool!   ---- deleted -----   you: You are right, man!     So, yes, editing could be abused as you suggest, but discontinuities can occur already because of deletions (and as someone else mentioned, because upvoted comments get prioritized upward).  As for Jeff's argument about rate limiting, I agree that is important, but I don't understand why you can't just use a CAPTCHA to prevent too many edits in a short period of time. Unity doesn't load, no Launcher, no Dash appears How do I color intersection of two ellipses in different color. For instances, the ellipses should themselves be colored as yellow and their intersection as red. My code for drawing ellipses is given below  \draw (-4,0) ellipse (8 and 3); \draw (8,0) ellipse (8 and 3);   UPDATE: In the comments to individual answers, I have requested to show it for three ellipses. This is Baby Rudin exercise 7 of Chapter 3. Prove that the convergence of $\sum{a_n}$ implies the convergence of $\sum{\sqrt {a_k} \over k}$ if $a_n \ge 0$.  Proof:  I will attempt to show that the cauchy criterion is met so $${\sum_{k=n}^m {\sqrt {a_k} \over k}} \le \epsilon $$ for all $n,m \le N_1$. Im disregarding the absolute value since its all positive terms.   Since $\sum{a_n}$ converges, we know that the $\lim \limits_{n \to \infty} a_n =0$ So there exists some $N_2$ such that for all $n \ge N_2$, $$   a_n \lt \ {{(m-n)}^2k^2(\epsilon)^2} $$ I am again disregarding the absolute values because its always positive Let N=max{$N_1,N_2$} then for all $n,m \ge N$ $$\sum_{k=n}^m {\sqrt {a_k} \over k} \le \sum_{k=n}^m {\sqrt {{(m-n)}^2k^2(\epsilon)^2} \over k} \le \sum_{k=n}^m{(m-n)(\epsilon)} = \epsilon $$  Maybe this is just crazy, should I just use Cauchy-Schwarz inequality and forget about this or could I possibly make this method work? I've a set of regions within a city. I'd like to split each region into five subregions and then get the centroid of each one of them.  I know how to make a vector grid, but the problem I have is that the generated points are not taking into account the regions, they're only related to the general map.  I have this:    And I want to split each region in five equal size areas. Something like this:    I'd like to build a visualization similar to this one: . In order to accomplish that, I need to split each region, because the original ones are pretty big.