Inverse htmlentities / html_entity_decode - php

Question

Basically I want to turn a string like this:
<code> <div> blabla </div> </code>
into this:
<code> <div> blabla </div> </code>
How can I do it?
The use case (bc some people were curious):
A page like this with a list of allowed HTML tags and examples. For example, <code> is a allowed tag, and this would be the sample:
<code><?php echo "Hello World!"; ?></code>
I wanted a reverse function because there are many such tags with samples that I store them all into a array which I iterate in one loop, instead of handling each one individually...

Answer 1

My version using regular expressions:
$string = '<code> <div> blabla </div> </code>';
$new_string = preg_replace(
'/(.*?)(<.*?>|$)/se',
'html_entity_decode("$1").htmlentities("$2")',
$string
);
It tries to match every tag and textnode and then apply htmlentities and html_entity_decode respectively.

Answer 2

There isn't an existing function, but have a look at this.
So far I've only tested it on your example, but this function should work on all htmlentities
function html_entity_invert($string) {
$matches = $store = array();
preg_match_all('/(&(#?\w){2,6};)/', $string, $matches, PREG_SET_ORDER);
foreach ($matches as $i => $match) {
$key = '__STORED_ENTITY_' . $i . '__';
$store[$key] = html_entity_decode($match[0]);
$string = str_replace($match[0], $key, $string);
}
return str_replace(array_keys($store), $store, htmlentities($string));
}
Update:
Thanks to #Mike for taking the time to test my function with other strings. I've updated my regex from /(\&(.+)\;)/ to /(\&([^\&\;]+)\;)/ which should take care of the issue he raised.
I've also added {2,6} to limit the length of each match to reduce the possibility of false positives.
Changed regex from /(\&([^\&\;]+){2,6}\;)/ to /(&([^&;]+){2,6};)/ to remove unnecessary excaping.
Whooa, brainwave! Changed the regex from /(&([^&;]+){2,6};)/ to /(&(#?\w){2,6};)/ to reduce probability of false positives even further!

Answer 3

Replacing alone will not be good enough for you. Whether it be regular expressions or simple string replacing, because if you replace the &lt &gt signs then the < and > signs or vice versa you will end up with one encoding/decoding (all &lt and &gt or all < and > signs).
So if you want to do this, you will have to parse out one set (I chose to replace with a place holder) do a replace then put them back in and do another replace.
$str = "<code> <div> blabla </div> </code>";
$search = array("<",">",);
//place holder for < and >
$replace = array("[","]");
//first replace to sub out < and > for [ and ] respectively
$str = str_replace($search, $replace, $str);
//second replace to get rid of original < and >
$search = array("<",">");
$replace = array("<",">",);
$str = str_replace($search, $replace, $str);
//third replace to turn [ and ] into < and >
$search = array("[","]");
$replace = array("<",">");
$str = str_replace($search, $replace, $str);
echo $str;

Answer 4

I think i have a small sollution, why not break html tags into an array and then compare and change if needed?
function invertHTML($str) {
$res = array();
for ($i=0, $j=0; $i < strlen($str); $i++) {
if ($str{$i} == "<") {
if (isset($res[$j]) && strlen($res[$j]) > 0){
$j++;
$res[$j] = '';
} else {
$res[$j] = '';
}
$pos = strpos($str, ">", $i);
$res[$j] .= substr($str, $i, $pos - $i+1);
$i += ($pos - $i);
$j++;
$res[$j] = '';
continue;
}
$res[$j] .= $str{$i};
}
$newString = '';
foreach($res as $html){
$change = html_entity_decode($html);
if($change != $html){
$newString .= $change;
} else {
$newString .= htmlentities($html);
}
}
return $newString;
}
Modified .... with no errors.

Answer 5

So, although other people on here have recommended regular expressions, which may be the absolute right way to go ... I wanted to post this, as it is sufficient for the question you asked.
Assuming that you are always using html'esque code:
$str = '<code> <div> blabla </div> </code>';
xml_parse_into_struct(xml_parser_create(), $str, $nodes);
$xmlArr = array();
foreach($nodes as $node) {
echo htmlentities('<' . $node['tag'] . '>') . html_entity_decode($node['value']) . htmlentities('</' . $node['tag'] . '>');
}
Gives me the following output:
<CODE> <div> blabla </div> </CODE>
Fairly certain that this wouldn't support going backwards again .. as other solutions posted, would, in the sense of:
$orig = '<code> <div> blabla </div> </code>';
$modified = '<CODE> <div> blabla </div> </CODE>';
$modifiedAgain = '<code> <div> blabla </div> </code>';

Answer 6

I'd recommend using a regular expression, e.g. preg_replace():
http://www.php.net/manual/en/function.preg-replace.php
http://www.webcheatsheet.com/php/regular_expressions.php
http://davebrooks.wordpress.com/2009/04/22/php-preg_replace-some-useful-regular-expressions/

Answer 7

Edit: It appears that I haven't fully answered your question. There is no built-in PHP function to do what you want, but you can do find and replace with regular expressions or even simple expressions: str_replace, preg_replace