PHP: htmlspecialchars

Description

string htmlspecialchars ( string string [, int quote_style [, string charset]] )

Certain characters have special significance in HTML, and should be represented by HTML entities if they are to preserve their meanings. This function returns a string with some of these conversions made; the translations made are those most useful for everyday web programming. If you require all HTML character entities to be translated, use htmlentities() instead.

This function is useful in preventing user-supplied text from containing HTML markup, such as in a message board or guest book application. The optional second argument, quote_style, tells the function what to do with single and double quote characters. The default mode, ENT_COMPAT, is the backwards compatible mode which only translates the double-quote character and leaves the single-quote untranslated. If ENT_QUOTES is set, both single and double quotes are translated and if ENT_NOQUOTES is set neither single nor double quotes are translated.

The translations performed are:

'&' (ampersand) becomes '&'
'"' (double quote) becomes '"' when ENT_NOQUOTES is not set.
''' (single quote) becomes ''' only when ENT_QUOTES is set.
'<' (less than) becomes '<'
'>' (greater than) becomes '>'

Przykład 1. htmlspecialchars() example


<?php

$new = htmlspecialchars("<a href='test'>Test</a>", ENT_QUOTES);

echo $new; // &lt;a href=&#039;test&#039;&gt;Test&lt;/a&gt;

?>

Note that this function does not translate anything beyond what is listed above. For full entity translation, see htmlentities(). Support for the optional second argument was added in PHP 3.0.17 and PHP 4.0.3.

The third argument charset defines character set used in conversion. The default character set is ISO-8859-1. Support for this third argument was added in PHP 4.1.0.

Following character sets are supported in PHP 4.3.0 and later.

Tabela 1. Supported charsets

Charset	Aliases	Description
ISO-8859-1	ISO8859-1	Western European, Latin-1
ISO-8859-15	ISO8859-15	Western European, Latin-9. Adds the Euro sign, French and Finnish letters missing in Latin-1(ISO-8859-1).
UTF-8		ASCII compatible multi-byte 8-bit Unicode.
cp866	ibm866, 866	DOS-specific Cyrillic charset. This charset is supported in 4.3.2.
cp1251	Windows-1251, win-1251, 1251	Windows-specific Cyrillic charset. This charset is supported in 4.3.2.
cp1252	Windows-1252, 1252	Windows specific charset for Western European.
KOI8-R	koi8-ru, koi8r	Russian. This charset is supported in 4.3.2.
BIG5	950	Traditional Chinese, mainly used in Taiwan.
GB2312	936	Simplified Chinese, national standard character set.
BIG5-HKSCS		Big5 with Hong Kong extensions, Traditional Chinese.
Shift_JIS	SJIS, 932	Japanese
EUC-JP	EUCJP	Japanese

Notatka: Any other character sets are not recognized and ISO-8859-1 will be used instead.

User Contributed Notes


I am not sure, maybe I'm missing something, but I have found something interesting:

I've been working on a project, where I had to use htmlspecialchars (for opbvious reasons). I olso needed to de-code the encoded string. What I have done was almost a copy and paste from php.net:

$trans=get_html_translation_table(HTML_SPECIALCHARS, ENT_QUOTES);

$trans=array_flip($trans);

$string=strtr($encoded, $trans);

(it looked a bit different in my code, but the idea is clear)

I couldn't get the apostrophe sign de-coded, and I needed it for the <A> tags. After an hour or so of debuging, I decided do print_r($trans). What I got was:

...

[&#39;] => '

...

BUT the apostrophe was encoded to $#039; -> note the zero.

I don't suppose it's a bug, but it definetely IS a potential pitfall, watch out for this one.


Hello,



If you are getting trouble to SGDB write/read HTML data, try to use this:



<?php



//from html_entity_decode() manual page

function unhtmlentities ($string) {

   $trans_tbl =get_html_translation_table (HTML_ENTITIES );

   $trans_tbl =array_flip ($trans_tbl );

   return strtr ($string ,$trans_tbl );

}



//read from db

$content = stripslashes (htmlspecialchars ($field['content']));



//write to db

$content = unhtmlentities (addslashes (trim ($_POST['content'])));



//make sure result of function get_magic_quotes_gpc () == 0, you can get strange slashes in your content adding slashes twice



//better to do this using addslashes

$content = (! get_magic_quotes_gpc ()) ? addslashes ($content) : $content;



?>


I have found that this regular expression is sufficient for making sure that existing character entities show after htmlspecialchars() replaces _all_ occurrences of & with the &amp; entity.



<?php

// Note: hsc is an abbreviation of htmlspecialchars

function hscFixed($str)

{

    return preg_replace("/&amp;(#[0-9]+|[a-z]+);/i", "&$1;", htmlspecialchars($str));

}

?>



The only flaw I can think of is if you have text of the vein; "&[word];", that is not meant to be a character but rather uses the ampersand and semicolon in their traditional grammatical denotations.  However I think this is highly unlikely to occur (among other reasons, the fact that anyone with enough grammatical inclination to use them as such probably won't leave out the space between the ampersand and the word).