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  • What ways are there for cleaning an R environment from objects?

    - by Tal Galili
    I know I can use ls() and rm() to see and remove objects that exist in my environment. However, when dealing with "old" .RData file, one needs to sometimes pick an environment a part to find what to keep and what to leave out. What I would like to do, is to have a GUI like interface to allow me to see the objects, sort them (for example, by there size), and remove the ones I don't need (for example, by a check-box interface). Since I imagine such a system is not currently implemented in R, what ways do exist? What do you use for cleaning old .RData files? Thanks, Tal

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  • Increasing your efficiency during programming

    - by Tom
    Yeah, yeah, I know, it is a little bit of offtopic, but let's try. So, I want to increase my efficiency during my programming as much as possible to programme as fast and sensibly as possiblle. What do you do before starting coding? Drink a lot of coffee, energy drinks? Do you listen to music during programming or you keep quite? Share your ideas.

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  • Is str.replace(..).replace(..) ad nauseam a standard idiom in Python?

    - by meeselet
    For instance, say I wanted a function to escape a string for use in HTML (as in Django's escape filter): def escape(string): """ Returns the given string with ampersands, quotes and angle brackets encoded. """ return string.replace('&', '&amp;').replace('<', '&lt;').replace('>', '&gt;').replace("'", '&#39;').replace('"', '&quot;') This works, but it gets ugly quickly and appears to have poor algorithmic performance (in this example, the string is repeatedly traversed 5 times). What would be better is something like this: def escape(string): """ Returns the given string with ampersands, quotes and angle brackets encoded. """ # Note that ampersands must be escaped first; the rest can be escaped in # any order. return replace_multi(string.replace('&', '&amp;'), {'<': '&lt;', '>': '&gt;', "'": '&#39;', '"': '&quot;'}) Does such a function exist, or is the standard Python idiom to use what I wrote before?

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  • Custom User Management for Google App Engine Java

    - by Gopi
    I am using GAE Java for a multi-user application. There are multiple users with different roles. Each user can login, do some operations and logout. The business restricts me from using Google User Service and I need to implement my own for authentication and session management. Can anyone please share with me how should I go about implementing my own user management? I have read its very tricky to implement own user management. Any pointers in terms of best approaches/ design / existing frameworks if any ? I could see some similar posts but they are for python.

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  • Why should I use a container div in HTML?

    - by lara.robertson
    I am currently learning html/css, and have noticed a common technique is to place a generic container div in the root of the body tag: <html> <head> ... </head> <body> <div id="container"> ... </div> </body> </html> Is there a valid reason for doing this? Why can't the css just reference the body tag?

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  • What are some good ways to write PHP application with modules support?

    - by Gabriel
    Hi, I'm starting to write a application in php with one of my friends and was wondering, if you have any advice on how to implement module support into our application. Or is there a way how to automatically load modules written in php by a php application? Or should i just rely on __autoload function? And we are not using any kind of framework, for now at least.

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  • TDD - beginner problems and stumbling blocks

    - by Noufal Ibrahim
    While I've written unit tests for most of the code I've done, I only recently got my hands on a copy of TDD by example by Kent Beck. I have always regretted certain design decisions I made since they prevented the application from being 'testable'. I read through the book and while some of it looks alien, I felt that I could manage it and decided to try it out on my current project which is basically a client/server system where the two pieces communicate via. USB. One on the gadget and the other on the host. The application is in Python. I started off and very soon got entangled in a mess of rewrites and tiny tests which I later figured didn't really test anything. I threw away most of them and and now have a working application for which the tests have all coagulated into just 2. Based on my experiences, I have a few questions which I'd like to ask. I gained some information from http://stackoverflow.com/questions/1146218/new-to-tdd-are-there-sample-applications-with-tests-to-show-how-to-do-tdd but have some specific questions which I'd like answers to/discussion on. Kent Beck uses a list which he adds to and strikes out from to guide the development process. How do you make such a list? I initially had a few items like "server should start up", "server should abort if channel is not available" etc. but they got mixed and finally now, it's just something like "client should be able to connect to server" (which subsumed server startup etc.). How do you handle rewrites? I initially selected a half duplex system based on named pipes so that I could develop the application logic on my own machine and then later add the USB communication part. It them moved to become a socket based thing and then moved from using raw sockets to using the Python SocketServer module. Each time things changed, I found that I had to rewrite considerable parts of the tests which was annoying. I'd figured that the tests would be a somewhat invariable guide during my development. They just felt like more code to handle. I needed a client and a server to communicate through the channel to test either side. I could mock one of the sides to test the other but then the whole channel wouldn't be tested and I worry that I'd miss that. This detracted from the whole red/green/refactor rhythm. Is this just lack of experience or am I doing something wrong? The "Fake it till you make it" left me with a lot of messy code that I later spent a lot of time to refactor and clean up. Is this the way things work? At the end of the session, I now have my client and server running with around 3 or 4 unit tests. It took me around a week to do it. I think I could have done it in a day if I were using the unit tests after code way. I fail to see the gain. I'm looking for comments and advice from people who have implemented large non trivial projects completely (or almost completely) using this methodology. It makes sense to me to follow the way after I have something already running and want to add a new feature but doing it from scratch seems to tiresome and not worth the effort. P.S. : Please let me know if this should be community wiki and I'll mark it like that. Update 0 : All the answers were equally helpful. I picked the one I did because it resonated with my experiences the most. Update 1: Practice Practice Practice!

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  • When to alter a function vs when to just write a new one...?

    - by Andrew Heath
    /is n00b Through the gift of knowledge and expertise encoded here, I am doing my best to avoid n00b mistakes as I learn the basics of programming. I use functions when I (think I) can in PHP, and keep them somewhat sorted in different includes. The n00b problem I'm running into now is situations where perhaps 4/5th of an existing function is relevant to a new need. Maybe there are a slightly different set of inputs, or an additional calculation or two in the series, or output needs a different format/structure... but the core of the function is still applicable. Is there a good rule of thumb regarding when one should bolt-on crap to an original function and when one should (literally) copy & paste most of it into a new function and tweak to fit the situation? On the one hand I feel bad duping code, on the other I feel bad cluttering up an existing function with stuff not always needed...

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  • In a PHP project, how do you organize and access your helper objects?

    - by Pekka
    How do you organize and manage your helper objects like the database engine, user notification, error handling and so on in a PHP based, object oriented project? Say I have a large PHP CMS. The CMS is organized in various classes. A few examples: the database object user management an API to create/modify/delete items a messaging object to display messages to the end user a context handler that takes you to the right page a navigation bar class that shows buttons a logging object possibly, custom error handling etc. I am dealing with the eternal question, how to best make these objects accessible to each part of the system that needs it. my first apporach, many years ago was to have a $application global that contained initialized instances of these classes. global $application; $application->messageHandler->addMessage("Item successfully inserted"); I then changed over to the Singleton pattern and a factory function: $mh =&factory("messageHandler"); $mh->addMessage("Item successfully inserted"); but I'm not happy with that either. Unit tests and encapsulation become more and more important to me, and in my understanding the logic behind globals/singletons destroys the basic idea of OOP. Then there is of course the possibility of giving each object a number of pointers to the helper objects it needs, probably the very cleanest, resource-saving and testing-friendly way but I have doubts about the maintainability of this in the long run. Most PHP frameworks I have looked into use either the singleton pattern, or functions that access the initialized objects. Both fine approaches, but as I said I'm happy with neither. I would like to broaden my horizon on what is possible here and what others have done. I am looking for examples, additional ideas and pointers towards resources that discuss this from a long-term, real-world perspective. Also, I'm interested to hear about specialized, niche or plain weird approaches to the issue. Bounty I am following the popular vote in awarding the bounty, the answer which is probably also going to give me the most. Thank you for all your answers!

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  • Counting down to zero in contrast to counting up to length - 1

    - by Helper Method
    Is it recommended to count in small loops (where possible) down from length - 1 to zero instead of counting up to length - 1? 1.) Counting down for (int i = a.length - 1; i >= 0; i--) { if (a[i] == key) return i; } 2.) Counting up for (int i = 0; i < a.length; i++) { if (a[i] == key) return i; } The first one is slightly faster that the second one (because comparing to zero is faster) but is a little more error-prone in my opinion. Besides, the first one could maybe not be optimized by future improvements of the JVM. Any ideas on that?

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  • Using an image file vs data URI in the CSS

    - by fudgey
    I'm trying to decide the best way to include an image that is required for a script I've written. I discovered this site and it made me think about trying this method to include the image as a data URI since it was so small - it's a 1x1 pixel 50% opacity png file (used for a background) - it ends up at 2,792 bytes as an image versus 3,746 bytes as text in the CSS. So would this be considered good practice, or would it just clutter up the CSS unnecessarily?

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  • Usage of Assert.Inconclusive

    - by Johannes Rudolph
    Hi, Im wondering how someone should use Assert.Inconclusive(). I'm using it if my Unit test would be about to fail for a reason other than what it is for. E.g. i have a method on a class that calculates the sum of an array of ints. On the same class there is also a method to calculate the average of the element. It is implemented by calling sum and dividing it by the length of the array. Writing a Unit test for Sum() is simple. However, when i write a test for Average() and Sum() fails, Average() is likely to fail also. The failure of Average is not explicit about the reason it failed, it failed for a reason other than what it should test for. That's why i would check if Sum() returns the correct result, otherwise i Assert.Inconclusive(). Is this to be considered good practice? What is Assert.Inconclusive intended for? Or should i rather solve the previous example by means of an Isolation Framework?

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  • What can be improved in this PHP code?

    - by Noctis Skytower
    This is a custom encryption library. I do not know much about PHP's standard library of functions and was wondering if the following code can be improved in any way. The implementation should yield the same results, the API should remain as it is, but ways to make is more PHP-ish would be greatly appreciated. Code <?php /*************************************** Create random major and minor SPICE key. ***************************************/ function crypt_major() { $all = range("\x00", "\xFF"); shuffle($all); $major_key = implode("", $all); return $major_key; } function crypt_minor() { $sample = array(); do { array_push($sample, 0, 1, 2, 3); } while (count($sample) != 256); shuffle($sample); $list = array(); for ($index = 0; $index < 64; $index++) { $b12 = $sample[$index * 4] << 6; $b34 = $sample[$index * 4 + 1] << 4; $b56 = $sample[$index * 4 + 2] << 2; $b78 = $sample[$index * 4 + 3]; array_push($list, $b12 + $b34 + $b56 + $b78); } $minor_key = implode("", array_map("chr", $list)); return $minor_key; } /*************************************** Create the SPICE key via the given name. ***************************************/ function named_major($name) { srand(crc32($name)); return crypt_major(); } function named_minor($name) { srand(crc32($name)); return crypt_minor(); } /*************************************** Check validity for major and minor keys. ***************************************/ function _check_major($key) { if (is_string($key) && strlen($key) == 256) { foreach (range("\x00", "\xFF") as $char) { if (substr_count($key, $char) == 0) { return FALSE; } } return TRUE; } return FALSE; } function _check_minor($key) { if (is_string($key) && strlen($key) == 64) { $indexs = array(); foreach (array_map("ord", str_split($key)) as $byte) { foreach (range(6, 0, 2) as $shift) { array_push($indexs, ($byte >> $shift) & 3); } } $dict = array_count_values($indexs); foreach (range(0, 3) as $index) { if ($dict[$index] != 64) { return FALSE; } } return TRUE; } return FALSE; } /*************************************** Create encode maps for encode functions. ***************************************/ function _encode_map_1($major) { return array_map("ord", str_split($major)); } function _encode_map_2($minor) { $map_2 = array(array(), array(), array(), array()); $list = array(); foreach (array_map("ord", str_split($minor)) as $byte) { foreach (range(6, 0, 2) as $shift) { array_push($list, ($byte >> $shift) & 3); } } for ($byte = 0; $byte < 256; $byte++) { array_push($map_2[$list[$byte]], chr($byte)); } return $map_2; } /*************************************** Create decode maps for decode functions. ***************************************/ function _decode_map_1($minor) { $map_1 = array(); foreach (array_map("ord", str_split($minor)) as $byte) { foreach (range(6, 0, 2) as $shift) { array_push($map_1, ($byte >> $shift) & 3); } } return $map_1; }function _decode_map_2($major) { $map_2 = array(); $temp = array_map("ord", str_split($major)); for ($byte = 0; $byte < 256; $byte++) { $map_2[$temp[$byte]] = chr($byte); } return $map_2; } /*************************************** Encrypt or decrypt the string with maps. ***************************************/ function _encode($string, $map_1, $map_2) { $cache = ""; foreach (str_split($string) as $char) { $byte = $map_1[ord($char)]; foreach (range(6, 0, 2) as $shift) { $cache .= $map_2[($byte >> $shift) & 3][mt_rand(0, 63)]; } } return $cache; } function _decode($string, $map_1, $map_2) { $cache = ""; $temp = str_split($string); for ($iter = 0; $iter < strlen($string) / 4; $iter++) { $b12 = $map_1[ord($temp[$iter * 4])] << 6; $b34 = $map_1[ord($temp[$iter * 4 + 1])] << 4; $b56 = $map_1[ord($temp[$iter * 4 + 2])] << 2; $b78 = $map_1[ord($temp[$iter * 4 + 3])]; $cache .= $map_2[$b12 + $b34 + $b56 + $b78]; } return $cache; } /*************************************** This is the public interface for coding. ***************************************/ function encode_string($string, $major, $minor) { if (is_string($string)) { if (_check_major($major) && _check_minor($minor)) { $map_1 = _encode_map_1($major); $map_2 = _encode_map_2($minor); return _encode($string, $map_1, $map_2); } } return FALSE; } function decode_string($string, $major, $minor) { if (is_string($string) && strlen($string) % 4 == 0) { if (_check_major($major) && _check_minor($minor)) { $map_1 = _decode_map_1($minor); $map_2 = _decode_map_2($major); return _decode($string, $map_1, $map_2); } } return FALSE; } ?> This is a sample showing how the code is being used. Hex editors may be of help with the input / output. Example <?php # get and process all of the form data @ $input = htmlspecialchars($_POST["input"]); @ $majorname = htmlspecialchars($_POST["majorname"]); @ $minorname = htmlspecialchars($_POST["minorname"]); @ $majorkey = htmlspecialchars($_POST["majorkey"]); @ $minorkey = htmlspecialchars($_POST["minorkey"]); @ $output = htmlspecialchars($_POST["output"]); # process the submissions by operation # CREATE @ $operation = $_POST["operation"]; if ($operation == "Create") { if (strlen($_POST["majorname"]) == 0) { $majorkey = bin2hex(crypt_major()); } if (strlen($_POST["minorname"]) == 0) { $minorkey = bin2hex(crypt_minor()); } if (strlen($_POST["majorname"]) != 0) { $majorkey = bin2hex(named_major($_POST["majorname"])); } if (strlen($_POST["minorname"]) != 0) { $minorkey = bin2hex(named_minor($_POST["minorname"])); } } # ENCRYPT or DECRYPT function is_hex($char) { if ($char == "0"): return TRUE; elseif ($char == "1"): return TRUE; elseif ($char == "2"): return TRUE; elseif ($char == "3"): return TRUE; elseif ($char == "4"): return TRUE; elseif ($char == "5"): return TRUE; elseif ($char == "6"): return TRUE; elseif ($char == "7"): return TRUE; elseif ($char == "8"): return TRUE; elseif ($char == "9"): return TRUE; elseif ($char == "a"): return TRUE; elseif ($char == "b"): return TRUE; elseif ($char == "c"): return TRUE; elseif ($char == "d"): return TRUE; elseif ($char == "e"): return TRUE; elseif ($char == "f"): return TRUE; else: return FALSE; endif; } function hex2bin($str) { if (strlen($str) % 2 == 0): $string = strtolower($str); else: $string = strtolower("0" . $str); endif; $cache = ""; $temp = str_split($str); for ($index = 0; $index < count($temp) / 2; $index++) { $h1 = $temp[$index * 2]; if (is_hex($h1)) { $h2 = $temp[$index * 2 + 1]; if (is_hex($h2)) { $cache .= chr(hexdec($h1 . $h2)); } else { return FALSE; } } else { return FALSE; } } return $cache; } if ($operation == "Encrypt" || $operation == "Decrypt") { # CHECK FOR ANY ERROR $errors = array(); if (strlen($_POST["input"]) == 0) { $output = ""; } $binmajor = hex2bin($_POST["majorkey"]); if (strlen($_POST["majorkey"]) == 0) { array_push($errors, "There must be a major key."); } elseif ($binmajor == FALSE) { array_push($errors, "The major key must be in hex."); } elseif (_check_major($binmajor) == FALSE) { array_push($errors, "The major key is corrupt."); } $binminor = hex2bin($_POST["minorkey"]); if (strlen($_POST["minorkey"]) == 0) { array_push($errors, "There must be a minor key."); } elseif ($binminor == FALSE) { array_push($errors, "The minor key must be in hex."); } elseif (_check_minor($binminor) == FALSE) { array_push($errors, "The minor key is corrupt."); } if ($_POST["operation"] == "Decrypt") { $bininput = hex2bin(str_replace("\r", "", str_replace("\n", "", $_POST["input"]))); if ($bininput == FALSE) { if (strlen($_POST["input"]) != 0) { array_push($errors, "The input data must be in hex."); } } elseif (strlen($bininput) % 4 != 0) { array_push($errors, "The input data is corrupt."); } } if (count($errors) != 0) { # ERRORS ARE FOUND $output = "ERROR:"; foreach ($errors as $error) { $output .= "\n" . $error; } } elseif (strlen($_POST["input"]) != 0) { # CONTINUE WORKING if ($_POST["operation"] == "Encrypt") { # ENCRYPT $output = substr(chunk_split(bin2hex(encode_string($_POST["input"], $binmajor, $binminor)), 58), 0, -2); } else { # DECRYPT $output = htmlspecialchars(decode_string($bininput, $binmajor, $binminor)); } } } # echo the form with the values filled echo "<P><TEXTAREA class=maintextarea name=input rows=25 cols=25>" . $input . "</TEXTAREA></P>\n"; echo "<P>Major Name:</P>\n"; echo "<P><INPUT id=textbox1 name=majorname value=\"" . $majorname . "\"></P>\n"; echo "<P>Minor Name:</P>\n"; echo "<P><INPUT id=textbox1 name=minorname value=\"" . $minorname . "\"></P>\n"; echo "<DIV style=\"TEXT-ALIGN: center\"><INPUT class=submit type=submit value=Create name=operation>\n"; echo "</DIV>\n"; echo "<P>Major Key:</P>\n"; echo "<P><INPUT id=textbox1 name=majorkey value=\"" . $majorkey . "\"></P>\n"; echo "<P>Minor Key:</P>\n"; echo "<P><INPUT id=textbox1 name=minorkey value=\"" . $minorkey . "\"></P>\n"; echo "<DIV style=\"TEXT-ALIGN: center\"><INPUT class=submit type=submit value=Encrypt name=operation> \n"; echo "<INPUT class=submit type=submit value=Decrypt name=operation> </DIV>\n"; echo "<P>Result:</P>\n"; echo "<P><TEXTAREA class=maintextarea name=output rows=25 readOnly cols=25>" . $output . "</TEXTAREA></P></DIV></FORM>\n"; ?> What should be editted for better memory efficiency or faster execution?

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  • Best practice with respect to NPE and multiple expressions on single line

    - by JRL
    I'm wondering if it is an accepted practice or not to avoid multiple calls on the same line with respect to possible NPEs, and if so in what circumstances. For example: getThis().doThat(); vs Object o = getThis(); o.doThat(); The latter is more verbose, but if there is an NPE, you immediately know what is null. However, it also requires creating a name for the variable and more import statements. So my questions around this are: Is this problem something worth designing around? Is it better to go for the first or second possibility? Is the creation of a variable name something that would have an effect performance-wise? Is there a proposal to change the exception message to be able to determine what object is null in future versions of Java ?

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  • What are the virtues of using XML comments in .NET?

    - by Michal Czardybon
    I can't understand the virtues of using XML comments. I know they can be converted into nice documentation external to the code, but the same can be achieved with the much more concise DOxygen syntax. In my opinion the XML comments are wrong, because: They obfuscate the comments and the code in general. (They are more difficult to read by humans). Less code can be viewed on a single screen, because "summary" and "/summary" take additional lines. They suggest that all method parameters have to be commented, whereas 90% of them are obvious and SHOULD be left not commented. The only problem I have with this is that my point of view seems to be in minority. Why?

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  • Any difference in compiler behavior for each of these snippets?

    - by HotHead
    Please consider following code: 1. uint16 a = 0x0001; if(a < 0x0002) { // do something } 2. uint16 a = 0x0001; if(a < uint16(0x0002)) { // do something } 3. uint16 a = 0x0001; if(a < static_cast<uint16>(0x0002)) { // do something } 4. uint16 a = 0x0001; uint16 b = 0x0002; if(a < b) { // do something } What compiler does in backgorund and what is the best (and correct) way to do above testing? p.s. sorry, but I couldn't find the better title :) EDIT: values 0x0001 and 0x0002 are only example. There coudl be any 2 byte value instead. Thank you in advance!

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  • how to wrap a function that only takes individual elements to make it take a list

    - by stevejb
    Hello, Say I have a function handed to me that I cannot change and must use as is. This function takes several objects in the form of oldFunction( object1, object2, object3, ...) where ... are other arguments. I want to write a wrapper to take a list of objects. My idea was this. sjb.ListWrapper <- function(myList,...) { lLen <- length(myList) myStr <- "" for( i in 1:lLen) { myStr <- paste(myStr, "myList[[", i , "]],",sep="") } myCode <- paste("oldFunction(", myStr, "...)") eval({myCode}) } However, the issue is that I want to use this from Sweave and I need the output of oldFunction to be printed. What is the right way to do this? Thanks.

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  • How atomic *should* I make an Ajax form?

    - by b. e. hollenbeck
    I have some web forms that I'm bringing over with AJAX, and as I was dealing with the database on the back end, I thought that it might be easier to just handle each input on the form atomically with AJAX, saving the form in 'real time' as the user edits it. The forms are ~20 fields of administrative settings. Would this create massive overhead with the app, cause it to be error-prone, or is this a feasible idea? Of course, contingent operations (like a checkbox that then requires a text entry) would be held until the textbox gained and lost focus. Comments?

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  • What are the weaknesses of this user authentication method?

    - by byronh
    I'm developing my own PHP framework. It seems all the security articles I have read use vastly different methods for user authentication than I do so I could use some help in finding security holes. Some information that might be useful before I start. I use mod_rewrite for my MVC url's. Passwords are sha1 and md5 encrypted with 24 character salt unique to each user. mysql_real_escape_string and/or variable typecasting on everything going in, and htmlspecialchars on everything coming out. Step-by step process: Top of every page: session_start(); session_regenerate_id(); If user logs in via login form, generate new random token to put in user's MySQL row. Hash is generated based on user's salt (from when they first registered) and the new token. Store the hash and plaintext username in session variables, and duplicate in cookies if 'Remember me' is checked. On every page, check for cookies. If cookies set, copy their values into session variables. Then compare $_SESSION['name'] and $_SESSION['hash'] against MySQL database. Destroy all cookies and session variables if they don't match so they have to log in again. If login is valid, some of the user's information from the MySQL database is stored in an array for easy access. So far, I've assumed that this array is clean so when limiting user access I refer to user.rank and deny access if it's below what's required for that page. I've tried to test all the common attacks like XSS and CSRF, but maybe I'm just not good enough at hacking my own site! My system seems way too simple for it to actually be secure (the security code is only 100 lines long). What am I missing? I've also spent alot of time searching for the vulnerabilities with mysql_real_escape string but I haven't found any information that is up-to-date (everything is from several years ago at least and has apparently been fixed). All I know is that the problem was something to do with encoding. If that problem still exists today, how can I avoid it? Any help will be much appreciated.

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