Screening of special characters. What special characters are escaped in regular formats? Php escape special characters html
To understand what to do without testing, it is necessary to accurately understand the chain of contexts through which the row passes. You indicate a row from the farthest side to the end point of recognition, which is memory, complete with parsing code for regular expression.
Remember how the memory row is formed: it can be a simple row in the middle of the code or a row of inputs in the command row, or it can be either an interactive command row, or a command row specified in a shell script file, or in the middle of a shell script. memory, written by the code, or a (row) argument during further evaluation, or a row to place the code, generated dynamically with any encapsulation.
Each context is assigned a number of symbols with special functionality.
If you want to pass a character literally, not using a special function (local to the context), then you have to escape it for the appropriate context... which may require some other escape characters that may need additional input from front context ( Oh). In addition, there may be such things as the encoding of characters (the most common is utf-8, which looks like ASCII for arcane characters, and can be further interpreted by the terminal according to your setup respect, then you can behave differently, the lower attribute is coded HTML/XML, which is necessary for the correct understanding of the process.
For example, a regular command line expression that starts with perl -npe may be passed to a set of system calls exec, which is connected as a channel that accesses a file, from these system calls exec simply sends a list of arguments that are separated ( not screened) gaps and possibly channels (|) and redirection (> N> N> & M), arms, interactive extensions * and? , $(()) ... (all these are special characters that are used in * sh, which can be created such that they are considered a regular symbol in the current context, but they are evaluated in order: before the command line. The command line is read by the program like bash /sh/csh /tcsh/zsh, essentially in the middle of a double foot or a single foot, the screen is simpler, but there is no need to put a row in the command row in the feet, which is why the gap is mainly due to starting with the prefix with the reverse row. and there is no need for a paw, In addition, the functionality of opening for the symbols * і? is not available, but it analyzes the context itself, as in the paw, then, when evaluating the command line, the regular virus, removing from memory (not as written in the command line), removes the same processing , which is in the output file.For a regular expression with square arms, there is a context for the character set, a regular perl expression can be placed with a large set of non-alpha numeric characters (for example, m//or m:/shorter/for/ways:.. .).
You have more details about the symbols in the other branch, which are even more specific to the end context of the regular expression. As I have already stated, you will guess that you are discovering that regexp is discarded by tests, which is likely due to the fact that a different context may contain a different set of characters, which will confuse your memory about the tests (often a backslash is a symbol , which It is used in other contexts to screen a literal character instead of its function.).
Author's view: I love you, friends. In this article we will talk about escaping special characters in regular formats. Under special characters, of course, metacharacters in regular expressions suffer. Shall we?
Also, as we already know from previous articles, regular expressions have no different metacharacters, which is where the whole range of regular expressions comes from. For example, one of the most commonly abused metasymbols is dot. The point in the standard mode of the pattern is matched with any symbol, in addition to the reversal of the row.
It’s amazing that if we need to know the point itself in the row, then using a metasymbol will give us the wrong result.
Instead of placing a point in a row, we removed the entire row from the inside. To solve the problem, it is necessary to indicate regularly that the dot is a special character, then. So that she runs away from herself. It is your responsibility to avoid using another metasymbol if you are aware of the backslash -.
Please note, this special symbol is used as an escape symbol in regular scripts, and in other language programming. So, let’s try putting a back slash before the dot.
The axis is now doing everything we need. So it’s our responsibility to escape any other metacharacters if necessary, so that they become familiar as primary characters and get away from themselves.
Well, that’s all I have for today. You can learn more about regular expressions in our course on regular expressions. Good luck!
The report from regular expressions has a section called " Meta characters (escaped) This is all about these meta symbols (they are also called special symbols) and what is mentioned in this article.
Special characters- these are symbols, such as letters and numbers. That's all symbols, besides letters and numbers.
Special symbols include symbols such as dot, star, plus, food, symbol and others.
As we know from previous articles, certain special characters play a special role in regular expressions. This is why a special symbol may appear as a manifestation.
For example, a dot means absolutely any symbol. The star is a quantifier that repeats from zero to infinity. Plus there is also a quantifier of repetition from one to infinity. The leading symbol ^ means the beginning of the row, and the dollar sign ($) means the end of the row. Before speech, the dollar symbol is also an obvious symbol. We also know that the symbol plays a different role because we place it in the middle of the square arms. We talked about all these important things in previous articles.
In this article I rely on the power supply How to use special characters in regular expression ".
In order to assign this special role to a special symbol in regular expression, it is necessary to ekranuvati. In this way, this special symbol is represented by the symbol itself, which is є. So the shielded dot means the dot itself, and not just any symbol. The missing star means the star itself, not the repetition quantifier.
Ekranuvannya struggle for help with the turnaround. In order to escape any special character, you need to put a trailing slash in front of it.
Let’s say we have a task like this: “Check whether the speck is placed at the end of the row.” So, in order for this point in a regular expression to be the point itself, and not some other symbol, it must be screened.
Var str = "Vin is a hero."; var reg = /.*\.$/; alert(reg.test(str)); // true
Most importantly, the result of checking the row for consistency with regular detection is true. If we remove the speck from the end of the row, the result will still be false.
Other special characters are displayed in the same way.
Var str = "x+y=.n*m=/,co\la"; var reg = /x\+y=\.n\*m=\/,co\\la/; alert(reg.test(str)); // true
Here we have expanded the screens for the symbols plus (\+), dots (\.), stars (\*), leading slash (\/) and leading slash (\\\). Please note that the backslash is written in a row with two backslashes. І is screened in the regular expression, also with the help of two converse characters.
If we use alert to display the row from the variable str, then instead of two backlashes we can only use one.
In the same way, all the symbols specified in the browser are displayed in the meta-symbols section.
And why, perhaps, must. You already know this little article How to escape special characters And how to avoid them in the formation of regular viruses.
Zavdannya
- Let’s say we need to check for consistency the following row: “I won $400.” Write a regular expression that checks the presence of the dollar symbol at the end of the row. Turn the row over to match.
3.1 Screening of special characters
First of all, when transferring variable form values in SQL queries, you need to use a special method to escape certain characters (accents, apostrophe), for example, put a trailing slash in front of them. The function assigned to insert is:
mysql_escape_string()
string mysql_escape_string(string $str)
The function is similar to the other function addslashes(), but it adds slashes before another set of special characters. Practice shows that for text data you can use the addslashes() function instead of mysql_escape_string(). There are a lot of scripts so I’m afraid.
The MySQL standard for escaping requires characters that are written in PHP like this: "\x00", "\n", "\r", "\", """, "" and "\x1A".
This number must contain a character with a null ASCII code, and mysql_escape_string() can be used not only for text data, but also for binary data. You can, for example, import a small GIF image (file_get_contents() function), and then insert it into the database, having first scanned all the special characters. When downloaded, the picture will appear to the person who first saw it.
Escaping symbols is just a way to write correct SQL statements, nothing more. Nothing is added to the data, and the data is saved in the database without additional slashes - just as it looked before it was screened.
From the mysql_escape_string() wiki, the code for the first step looks like this:
"DELETE FROM table WHERE name="".mysql_escape_string($name).""");
It's too long, it's ugly, it's ugly.
3.2 Query templates and placeholders
Let's look at the solution differently.
Instead of explicit screening and insertion of changeable entries, special markers (placeholders) are placed in their place, which is what they look like.
The very values that will be substituted for them are passed along with additional parameters.
Using the hypothetical function mysql_qwo, the code of which will be represented below, the front entry can be rewritten like this:
mysql_qw("DELETE FROM table WHERE name=?", $name);
It has become shorter and easier to steal: now, even when writing code, we cannot accidentally miss the call to the mysql_escape_string() function and, thus, be exposed to a hacker. All changes are performed automatically in the middle of the function.
The listing lib_mysql_qw.php has the simplest implementation of the mysql_qw() function (qw is a query wrapper).
There is also a library lib/Placeholder.php, which will provide a much stronger support for the language placeholders: http://dklab.ru/chicken/30.html.
In most situations there are sufficient possibilities for using the mysql_qw() function.
Listing lib_mysql_qw.php
// result-set, mysql_qw ($connection_id, $query, $argl, $arg2...).
// result-set mysql_qw($query, $argl, $arg2, ...)
// The function connects to MySQL via a connection specified as
// $connection_id (if it is not specified, then open it after the rest).
// The $query parameter can contain wildcards?,
// substitute values will be substituted
// arguments $arg1, $arg2, etc. (in order), escaped
// Included in apostrophes.
function mysql_qw()
// Remove all function arguments.
$args = func_get_args();
// Since the first parameter is of the “resource” type, it is an ID connection.
// Form is followed by a template.
// Call the SQL function.
// string mysql_make_qw($query, $argl, $arg2,...)
// This function forms the SQL query behind the $query template,
function mysql_make_qw()
$args = func_get_args();
// As a result, $args will also be changed.
// Now we screen all arguments except the first one.
foreach ($args as $i=>$v)
if (!$i) continue; // this is the template
if (is_int($v)) continue; // Integers do not need to be escaped
//For every incident, we remember the remaining 20 arguments are unacceptable
// values, so that at the same time, what is the number "?" overweight
// Parameters, the SQL query was modified (to help with setup).
for ($i=$c=count($args)-1; $i<$c+20; $i++)
//Form the SQL query.
If you add explanatory entries, the size of the lib_mysql_qw.php file will change as much as three times:
function mysql_qw()
$args = func_get_args();
if (is_resource($args)) $conn = array_shift($args);
$query = call_user_func_array("mysql_make_qw", $args);
return $conn!==null ? mysql_query($query, $conn): mysql_query($query);
function mysql_make_qw()
$args = func_get_args();
$tmp1 - str_replace("%", "%%", $tmp1);
$tmp1 = str_replace("?", "%s", $tmp1);
foreach ($args as $i=>$v)
if (!$i) continue;
if (is_int($v)) continue;
$args[$i] = """.mysql_escape_string($v).""";
for ($i=$c=count($args)-1; $i<$c+20; $i++)
$args[$i+1] = "UNKNOWN_PLACEHOLDER_$i";
return call_user_func_array("sprintf", $args);
The sprintf() function accepts the % character as a control character. To use this special action, you need to connect it to work with the function. Then? replaced by %s, for sprintf() this means “take the damn argument”.
For clarity of the tested code, the main function is divided into two; the code for replacing wildcards in the mysql_make_qw() function is shown.
The listing test_qw.php provides an example of how to look at SQL queries after inserting placeholders.
Listing test_qw.php
require_once "lib_mysql_qw.php";
require_once "mysql_connect.php";
// It's obvious that we are hackers...
$name = "" OR "1";
// Valid request.
echo mysql_make_qw("DELETE FROM people WHERE name=?", $name)."
";
// Unacceptable written.
echo mysql_make_qw("DELETE FROM people WHERE name=? OR ?, $name)."
";
// The axis looks like Vikonannya is asked.
mysql_qw("DELETE FROM people WHERE name=? OR ?", $name)
or die(mysql_error());
As a result, the script will generate the following page:
DELETE FROM people WHERE name="\" OR \"1"
DELETE FROM people WHERE name=" \ " OR \ " 1" OR id=UNKNOWN_PLACEHOLDER_l
Unknown column "UNKNOWN_PLACEHOLDER_1" in "where clause1
Slashes appeared before apostrophes in the data, and a placeholder, which “rejected” the function arguments, was replaced by the row UNKNOWN_PLACEHOLDER_l.
Now, any attempt to create such a command in advance is doomed to failure (as noted, the remaining diagnostic notifications generated by the click die()), which is an important help for the improvement of scenarios.
Apache by Russian language: If the cob side is opened, then Apache is installed correctly. ● Go to the Apache Web server window using the additional Windows operating system settings panel and finish the server using the [X] button in the upper right corner of the window. 1.3. Installing PHP You can download PHP distributions from the official website http://www.php.net/downloads.php from the Windows section.
You should create your own programs yourself. Present in ASP and PHP, present in XML. Creation of server scripts. The basis of any language for creating dynamic sites. Present in ASP and PHP, present in XML. Description of the data. An important feature is that it allows data to be presented in a single format and recorded in a single way. This is the case in ASP and PHP, and in XML. Reality...
I software solutions on which to base. Servers are located in server rooms. Servers are managed by system administrators. 2. Databases 2.1 Concepts of databases (DBs) The fundamentals of modern information technology are databases (DBs) and database management systems (DBMS), the role of which is a single method of saving, processing and accessing...
The installation showed the correctness of the approach taken. However, the work requires further development to organize permanent access for readers to bibliographic resources of local libraries via the Internet. Literature 1. Glushakov S.V., Lomotkov D.V. Basic data: Basic course. - K.: Abris, 2000. -504 p. 2. Jason Mainger. Java: Programming Fundamentals:...
Screening of symbols- Replacement of certain characters in the text with relevant text substitutions. One of the types of core sequences.
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✪ Creation and screening of rows. JavaScript Basics
✪ Key JavaScript sequences, escape and special characters
Subtitle
Viznachennya
Place your programming, text-based command interfaces, and your text layouts (HTML, TeX, wiki layout) on the right of the structured text, in which case the characters (and their combinations) are vikorized as caring, looking at the structure of the text. In a situation where it is necessary to vikorize such a symbol as the “primary symbol of the language”, stand still screen bath.
Mental screening can be divided into three types:
- Screening a single character
- Screening of a group of characters following the sequence of characters “start screen”, “end screen”
- Following the additional command sequence “start screen” and the “end screen” symbol, which is specified before starting the text that is screened.
The number of screens as a cause of spillage
Screening of characters is especially important when the text is generated automatically. The inclusion of additional row data before the text transfers obligatory screening of the core characters. At the same time, often real rows of such symbols are not misplaced, which allows the program to skip this operation entirely and select a simple program that correctly deals with “no matter how reasonable” row data. However, such a simple code may be used, because a third party (the author of personal data) denies the unauthorized ability to pour into structure generated text. The spillover becomes serious as the text of the creation is read by the program. Traditionally, such problems are faced by sophisticated systems that use SQL (SQL-injection) and HTML (Cross, Site, Scripting) languages.
Apply it
Screening a single symbol
- In our C programming, in the middle of the rows of screen symbols, there is an additional “ ” symbol placed before the escape symbol. (In this case, the symbol "\" can be escaped, then the combination "\\" is used to escape the backslash), this symbol is used to escape characters in the unix command line.
- In the Microsoft Windows command line, the escape of a portion of the characters is indicated by the “^” symbol placed before the character to be escaped.
Screening a group of symbols
- In python programming, the escape of a group of characters in a row is done by inserting the letter r (in English raw) before the row, so that the characters are escaped by sequences r" text that is being screened "
- In the display window, text can be displayed using additional pseudo tags.
і . If you need to write down the pseudo tag itself, avoid using wildcards ( ).
