Is this php code sanitization redundant or incorrect? Let's say  this code is executed after press the submit button in a form with purposes of sanitization:   &lt;?php $yourname = check_input(filter_input(INPUT_POST, 'yourname', FILTER_SANITIZE_STRING)); $email = check_input(filter_input(INPUT_POST, 'email', FILTER_SANITIZE_EMAIL)); $likeit = check_input(filter_input(INPUT_POST, 'likeit', FILTER_SANITIZE_STRING)); $comments = check_input(filter_input(INPUT_POST, 'comments', FILTER_SANITIZE_STRING));  function check_input($data) {     $data = trim($data) . stripslashes($data) . htmlspecialchars($data);     return $data; } ?&gt;   Taking in account that the filter_input function is being applied, is the check_input($data) function redundant in this case?
How can I sanitize user input with PHP? Is there a catchall function somewhere that works well for sanitizing user input for SQL injection and XSS attacks, while still allowing certain types of HTML tags?
Which novel involves vampires, burning satellites, space travel, and body modification? About a decade ago, I encountered a novel or a novella that I cannot locate.   The setting was Earth, about one century into the future.  I remember vampires and a mesh of satellites around the Earth that were burning up in the atmosphere.  This motivated a mission to deep space to find the intelligence responsible for the satellites.  Most of the novel focused on the crew of the mission &mdash; I recall that they were not "standard" humans.  They had modifications to their minds and bodies, possibly for the mission.  At the time, I had gone on a binge, reading many short stories, novellas, and novels in quick succession.  I fear that I might be combining several stories into one, especially the vampires and the deep-space first-contact mission, and so I am fully prepared for an answer of the form, "No such story exists."  Any assistance would be greatly appreciated. VirtualBox 5.0.40 crashes the whole host since update to kernel 4.13.0-26-generic Mental estimate for tangent of an angle (from $0$ to $90$ degrees) T-Shirt print resolution A net $\varphi : [0, \omega_1) \to M$ on a metric space $M$ converges $\iff \varphi$ is eventually constant I want to prove that      If $M$ is a metric space, then a net $\varphi : [0, \omega_1) \to M$ converges if and only if $\varphi$ is eventually constant. ($[0, \omega_1)$ is the set of ordinals less than $\omega_1$, where $\omega_1$ is the first uncountable ordinal, with the order topology).   $(\Leftarrow)$ is clear.  My trouble is with $(\Rightarrow)$. Suppose that $\varphi \rightarrow x$.  Let $U = \{ \alpha \in [0, \omega_1) \, \mid \varphi(\alpha) \neq x \}.$  If $U = \emptyset $ we are done, so assume $U \neq \emptyset$. Since $[0, \omega_1)$ is well ordered, there is a $\alpha_1 \in U$ such that $ \alpha_1 \leq \alpha \, \, \forall \alpha \in U.$  If $ U \setminus \alpha_1 = \emptyset$ we are done. If not, we repeat the procedure.  It is clear that if $card(U) = n$ for some $n \in \omega$ then we only have a finite set of ordinals $\{\alpha_1, \ldots, \alpha_n\}=U$ so $\varphi$ is constant for $\alpha &gt; \alpha_n.$  If $U$ is countably infinite, then $U = \{\alpha_n\}_{n \in \omega}$ and since $[0, \omega_1)$ is sequentially compact and the $\alpha_n$'s are countable ordinals  we obtain a convergent subsequence $\{\alpha_{n_k}\}$ of $U$ to some countable ordinal $\beta \in [0, \omega_1)$ $[\beta = \cup_{n_k \in \omega}\alpha_{n_k}???],$ hence $\varphi$ is constant for all $ \alpha &gt; \beta.$     But what if $U$ is uncountable?    Idea: If $U = [0, \omega_1),$ then since $\varphi \rightarrow x$, for every $n \in \omega$ there is $\alpha_n \in U$ such that $\alpha \geq \alpha_n \implies \varphi(\alpha) \in B_{\frac{1}{n}}(x).$ This is a countable sequence, so since $[0, \omega_1)$ is sequentially compact, there is a subsequence converging to a countable ordinal $\beta \in [0, \omega_1)$. Clearly, $\beta$ satisfies that $\phi(\beta) \in B_{\frac{1}{n}}$(x) for every $n \in \omega.$     We can conclude that $\varphi(\beta)= x$ right?   For if $\varphi(\beta) \neq x$, then taking $n$ such that $0 &lt; \frac{1}{n} &lt; d(x, \varphi(\beta)),$ we would have that $\varphi(\beta) \not \in B_{\frac{1}{n}}(x),$ contradicting the hypothesis.  I feel pretty confident about this, but If someone sees an error in the argument, please comment. Thanks. This question was asked in an entrance test for an undergraduate mathematics program today, held all over India.   Question: $f$ is a differentiable function in $[0,1]$ such that $f(f(x))=x$ and $f(0)=1$.  Find the value of $\int_{0}^{1} (x-f(x))^{2016} dx$.  I tried to solve it by substituting $f(f(x))$ in place of $x$, but could not proceed much further. Any hints or solutions will be appreciated. Within my web application directory, how can I change all my folder permissions to rwxr-xr-x (755)? And how can I change all file permissions to rw-r--r-- (644)? I want to change all folders and files including sub-sub files and folders.   I know the following command would change all files and folders but I want to discrimate between a file and a folder.  chmod -R 755 ./my_web_app_project Determining "level" of an NPC ally for purpose of budgeting encounter XP "FTL" Communication with Quantum Entanglement? Can quantum entanglement make sending a message, whether audio, video, or even Morse code, instantaneous between two points (faster than it could travel normally at the speed of light)?  Let me first be clear, my question is not whether a message can travel faster than light. I simply mean whether a message can be generated here and then a copy of that message heard over there sooner than the message would normally be received.  Say a large number of entangled pairs are generated. One half the particles are given to Jack and the opposite ones to Sally. Jack then hops on a ship and travels 8 months to Mars. Sally then manipulates her particles in the form of a message. Do the corresponding opposite particles get manipulated simultaneously so that Jack receives the message instantly instead of the 16 light-minutes for a classically transmitted message? Existence of a group isomorphism between $(\mathbb K,+)$ and $(\mathbb K^\times,\cdot)$ Let $(\mathbb K,+,\cdot)$ be a field. Is there a group isomorphism between $(\mathbb K,+)$ and $(\mathbb K^\times,\cdot) $ ?  The answer should clearly be negative. I tried to proceed via contradiction, but this has not led me very far. Since it's some kind of &quot;trick problem&quot;, I'm merely looking for hints. Learning ArcPy? Where can I start to learn ArcPy? How a module can override theme suggestion? Basically it was  but I'll reword it, as I don't want to define a new theme (reason was already given).  What I want to do: in my module I have a file node--attach.tpl.php which is a modifed version of node.tpl.php. Now I want that, if view_mode = 'attach' then this file is used. Also, theme should be allowed to override it with its own node--attach.tpl.php in theme folder. "log in to" or "log into" or "login to" When writing an instruction about connecting to a computer using ssh, telnet, etc., I'm not sure what spacing to use in this familiar spoken phrase:   "Log in to host.com" "Log into host.com" "Login to host.com"   Maybe this is entirely subjective or the realm of industry jargon, but I couldn't think of anywhere else to ask.  Any insight? Calculate limit with L'Hospital's rule I want to calculate the limit $\displaystyle{\lim_{x\rightarrow 0}\frac{x^2\cos \left (\frac{1}{x}\right )}{\sin x}}$.   I have done the following:    It holds that $\lim_{x\rightarrow 0}\frac{x^2\cos \left (\frac{1}{x}\right )}{\sin x}=\frac{0}{0}$.   So, we can use L'Hospital's rule:  \begin{align*}\lim_{x\rightarrow 0}\frac{x^2\cos \left (\frac{1}{x}\right )}{\sin x}&amp;=\lim_{x\rightarrow 0}\frac{x^2\cos \left (\frac{1}{x}\right )}{\sin x} \\ &amp;=\lim_{x\rightarrow 0}\frac{\left (x^2\cos \left (\frac{1}{x}\right )\right )'}{\left (\sin x\right )'} =\lim_{x\rightarrow 0}\frac{2x\cdot \cos \left (\frac{1}{x}\right )+x^2\cdot \left (-\sin \left (\frac{1}{x}\right )\right )\cdot \left (\frac{1}{x}\right )'}{\cos x} \\ &amp;=\lim_{x\rightarrow 0}\frac{2x\cdot \cos \left (\frac{1}{x}\right )-x^2\cdot \sin \left (\frac{1}{x}\right )\cdot \left (-\frac{1}{x^2}\right )}{\cos x} \\ &amp; =\lim_{x\rightarrow 0}\frac{2x\cdot \cos \left (\frac{1}{x}\right )+\sin \left (\frac{1}{x}\right )}{\cos x}=\lim_{x\rightarrow 0}\left (2x\cdot \cos \left (\frac{1}{x}\right )+\sin \left (\frac{1}{x}\right )\right ) \\ &amp; =\lim_{x\rightarrow 0}\left (2x\cdot \cos \left (\frac{1}{x}\right )\right )+\lim_{x\rightarrow 0}\left (\sin \left (\frac{1}{x}\right )\right )\end{align*}   We calculate the two limits separately   $\lim_{x\rightarrow 0}\left (2x\cdot \cos \left (\frac{1}{x}\right )\right )$ :    \begin{equation*}\left |\cos \left (\frac{1}{x}\right )\right |\leq 1 \Rightarrow -1\leq \cos \left (\frac{1}{x}\right )\leq 1  \Rightarrow -2x\leq 2x\cdot \cos \left (\frac{1}{x}\right )\leq  2x\end{equation*} we consider the limit $x\rightarrow 0$ and we get \begin{equation*}\lim_{x\rightarrow 0} \left (2x\cdot \cos \left (\frac{1}{x}\right ) \right )=0\end{equation*}    How can we calculate the limit $\lim_{x\rightarrow 0}\left (\sin \left (\frac{1}{x}\right )\right )$ ? It always takes a  and money to find the next . Why is it so important to do this work and what is the application those numbers? The add comment link and comment box overlaps bounty box The following you could have seen in  (sorry, I've commented there, so you won't see it anymore) in Chrome 35.0.1916.153 m (current version). Notice how the add comment link overlaps the bounty box:    The same you can observe with a comment box on other sites, e.g. at this time in :    Could you shift it a bit down ?  It seems that it happens on more than just Stack Overflow (maybe all sites ?). How can I  compare (without calculator or similar device) the values of $\pi^e$ and $e^\pi$ ? Minecraft directory doesn't have a 'Resource Packs' folder? I go into my .minecraft folder and there's Assets and all the other files and folders, but no resource packs folder?  If I create one manually, and place the textures inside, they don't show up in-game.  I'm on a Mac. I'm looking for a term for audio in form of the word visual.  Visual is defined as      of or relating to the sense of sight   What could you call the sense of hearing? Also, what do you call this form of a word? (i.e verb, noun...)  It should fit the x in the following sentence:     Is it possible to fall in love with someone without visual or x contact?   I'm not a native English speaker, so I couldn't find the terms for searching this. How can I prove that $$\displaystyle x-\frac {x^2} 2 &lt; \ln(1+x)$$ for any $x&gt;0$  I think it's somehow related to Taylor expansion of natural logarithm, when:  $$\displaystyle \ln(1+x)=\color{red}{x-\frac {x^2}2}+\frac {x^3}3 -\cdots$$  Can you please show me how? Thanks.