I'm running this query to fetch a post, if the member has access to it. Is it secure enough to just check if($row) ?  $sql = "SELECT f_title             FROM fields             INNER JOIN members                 ON m_group_id = f_group_id                 AND m_u_id = " . mysqli_real_escape_string($db_link, $_SESSION['u_id']) . "                 AND m_status &gt; 0             WHERE f_id = " . mysqli_real_escape_string($db_link, $_POST['id']) . "             LIMIT 1"; $result = mysqli_query($db_link, $sql) or die(mysqli_error($db_link)); $row = mysqli_fetch_assoc($result); if($row) {     echo 'Permission granted!'; } else {     echo 'Permission NOT granted!'; }
If user input is inserted without modification into an SQL query, then the application becomes vulnerable to , like in the following example:  $unsafe_variable = $_POST['user_input'];   mysql_query("INSERT INTO `table` (`column`) VALUES ('$unsafe_variable')");   That's because the user can input something like value'); DROP TABLE table;--, and the query becomes:  INSERT INTO `table` (`column`) VALUES('value'); DROP TABLE table;--')   What can be done to prevent this from happening?
I am trying to find a way with QGIS to get the intersection area of more than 2 layers.  All the tools in QGIS take just the 2 input layers.  For example in the image below, I have 4 layers and I want to retrieve just the black area.   Furthermore, I need to retrieve the count attribute and add it to the intersected area attribute table (in this case 4)    I know there is a tool that does the trick in ArcGIS, but is there a QGIS solution? How to change root password for mysql and phpmyadmin I've set up mysql and phpmyadmin and chose not to set a password when installing hoping that once set up i could login with root and no password but i get the following error from phpmyadmin:  Login without a password is forbidden by configuration (see AllowNoPassword)   I have previously moved the phpmyadmin folder to /var/www/   I have tried changing the following line  $cfg['Servers'][$i]['AllowNoPassword'] = false;   to  $cfg['Servers'][$i]['AllowNoPassword'] = true;   but still had no success, so i am wondering is there a way i can change the root passwords for both so i can access phpmyadmin and create databases. where is `cd` located? How much space does Ubuntu take up after it's already installed? I know how much space is required to install Ubuntu.  How much space does a Ubuntu installation take up on the disk? Inheriting Options? How to prove $\text{Rank}(AB)\leq \min(\text{Rank}(A), \text{Rank}(B))$? How to prove $\text{Rank}(AB)\leq \min(\text{Rank}(A), \text{Rank}(B))$? I could not install my modem driver so I have to update and install applications offline. For this I want to use keryx but to install keryx, Python and wxPython have to be installed first. So how do I install Python and wxPython offiline on Ubuntu 13.04?  Note : I don't have internet connection in Ubuntu. So I'll have to download the required file from my Windows 7. Can I use grep matches to execute command? I need to upgrade php from 5.3 to 5.4. I've installed it with rpm. I want clean install: delete all 5.3 packages, and install all necessary 5.4. Here is the command to see all installed packages:  rpm -qa |grep php   It prints out a list of packages, and I want to remove all them with:  rpm -e *pakage.name*   Can I iterate over all matches in grep results and use each match in:   rpm -e *grep.match* Schrödingers MySQL table: exists, yet it does not What award did Leia give Chewie, Han and Luke? What award/medal is this -  I have been searching  to try and find what medal this is, but i have not found it, does anyone know what this medal/award was and why it would be given (eg- bravery, serving in the battle of Yavin)? Use variable inside bash brace expansion I have a program that generates a variable number of pictures, ordered like that: 1.jpg, 2.jpg [...] 10.jpg..etc  I can't use *.jpg as input because the 10 will be processed before 2, 3, etc. so I want to use:  convert page_{1..$N}.jpg out.pdf   but does not work. How should the command be? Closure of a certain subset in a compact topological group Question about Angle-Preserving Operators This an exercise out of Spivak's "Calculus on Manifolds".  Edit:  There was a typo in the exercise as is noted below in the answers.  The statement has been edited to reflect this.  Given $x,y\in\mathbb{R}^{n}$, the angle between $x$ and $y$ is defined by  $$\angle(x,y) = \arccos\left(\frac{\langle x,y \rangle}{|x|\cdot |y|}\right),$$ where $\langle x,y \rangle$ denotes the standard Euclidean inner product.  A linear operator $T:\mathbb{R}^{n}\to\mathbb{R}^{n}$ is said to be angle-preserving if $\angle(T(x),T(y)) = \angle(x,y)$ for every $x,y\in\mathbb{R}^{n}$.  The exercise as stated:  Let $\{x_{1},\dots, x_{n}\}$ be a basis for $\mathbb{R}^{n}$.  Then suppose that $\lambda_{1}, \dots, \lambda_{n}\in \mathbb{R}$ are such that $Tx_{j} = \lambda_{j}x_{j}$ for each $j = 1,\dots, n$.  Then $T$ is angle-preserving only if (not if and only if!)$|\lambda_{i}| = |\lambda_{j}|$ for every $1\leq i\leq j\leq n$.  I'm having problems with the $(\Rightarrow)$ direction.  My best attempt (which seems to lead nowhere) is to suppose that $|\lambda_{j}|\neq |\lambda_{k}|$.  Then by assumption, \begin{align*} \angle(Tx_{j},Tx_{k}) &amp; = \arccos\left(\frac{\langle Tx_{j},Tx_{k} \rangle}{|Tx_{j}|\cdot |Tx_{k}|}\right)\\ &amp; = \arccos\left(\frac{\langle \lambda_{j}{x_{j}},\lambda_{k}{x_{k}} \rangle}{|\lambda_{j}{x_{j}}|\cdot |\lambda_{k}{x_{k}}|}\right)\\ &amp; = \arccos\left(\frac{\lambda_{j}\lambda_{k}\langle {x_{j}},{x_{k}} \rangle}{|\lambda_{j}|\cdot|\lambda_{k}|\cdot|{x_{j}}|\cdot |{x_{k}}|}\right)\\ &amp; = \arccos\left(\text{sign}(\lambda_{j})\text{sign}(\lambda_{k})\frac{\langle {x_{j}},{x_{k}} \rangle }{|{x_{j}}|\cdot |{x_{k}}|}\right)\\ \end{align*} may also be calculated as \begin{align*} \angle(Tx_{j},Tx_{k}) &amp; =  \angle(x_{j},x_{k})\\ &amp; = \arccos\left(\frac{\langle x_{j},x_{k} \rangle}{|x_{j}|\cdot |x_{k}|}\right). \end{align*}  Then since $\arccos$ is injective, I believe I can make the jump that $\text{sign}(\lambda_{j})\text{sign}(\lambda_{k}) = 1$, which does not resemble the conclusion that I should arrive at.  Note:  I wasn't sure what tag to put this under, so anyone who knows better please feel free to adjust.  Thanks for any help you can give. Do you have recommendations for books to self-teach Applied Statistics at the graduate level? I took several statistics courses in college but I found that my education was very theory driven.  I was wondering if any of you had a text in Applied Statistics (at the graduate level) that you recommend or have had good experience with. When does $120$ divide $n^5 - n$ Find n such that $n^5 - n$ is divisible by $120$. (*Here $n$ belongs to the natural number set)  Seems a trivial problem, but the answer mentioned in the text book seemed incomplete to me so I'm here just to ensure whether approach to this problem is correct or not.  So my approach is as follows: We know that $n^5 - n$ can be written as $n^5-n = n(n-1)(n+1)(n^2 + 1)$  Now since it's product of three consecutive natural numbers so it's divisible by $3! = 6$. Now using Fermat's Little theorem we can prove that $n^5= n \mod5$ hence $n^5 - n$ is divisible by $5$ as well. So $n^5 - n$ is divisible by $30$. Now to ensure their is another factor of $4$ in the term we need to ensure that $n^5 - n$ is divisible by $8$. I found that all odd natural numbers and multiples of $8$ makes $n^5 - n$ divisible by $8$, hence $n^5 - n$ is divisible by $120$. But in the text book they have only mentioned odd natural numbers as answer, which seemed incomplete to me.  Thanking everyone in advance:P Finding what methods a Python object has Given a Python object of any kind, is there an easy way to get the list of all methods that this object has?  Or,  if this is not possible, is there at least an easy way to check if it has a particular method other than simply checking if an error occurs when the method is called? I have a collection of articles written in latex, and I would like to "merge" them into a larger thesis document, in which each article will be a chapter. I have been looking at include and input, which are great if you start with the meta-document in mind. However in my articles I have sometimes a bit exotic dependencies, such as dot2texi, and using the naive approach fails rather abysmally with all kinds of broken paths.  So I was wondering, do you recommend any "best practices" for merging non-trivial documents -- which packages to look at, or to avoid at all cost, etc.  Thanks The Riemann zeta function $ζ(s)$ is defined for all complex numbers $s ≠ 1$ with a simple pole at $s = 1$. It has zeros at the negative even integers, i.e., at $s = −2, −4, −6, ...$.   My question: How one can obtain these roots. How would you count occurrences of a string (actually a char) within a string? JavaScript raises SyntaxError with data rendered in Jinja template