Re: Entity parsing

[Sam B. <bs...@us...>]

Hi Peter ,

Always's happy to have new ppl on board giving us a hand!  ;o) 
You seam to have some trouble with the Entity handling in Php.XPath.
I'm not quite sure if I understand the problem. But pleas read following
extract taken from Php.XPath's _translateAmpersand () function.
I think it's a good base to undersand the problematic.

  /**
   * Translate all ampersands to it's literal entities '&' and back.
   *
   * I wasn't aware of this problem at first but it's important to understand why we do this.
   * At first you must know:
   * a) PHP's XML parser *translates* all entities to the equivalent char E.g. &lt; is returned as '<'
   * b) PHP's XML parser (in V 4.1.0) has problems with most *literal* entities! The only one's that are 
   *    recognized are &amp;, &lt; &gt; and &quot;. *ALL* others (like &nbsp; &copy; a.s.o.) cause an 
   *    XML_ERROR_UNDEFINED_ENTITY error. I reported this as bug at http://bugs.php.net/bug.php?id=15092
   *    (It turned out not to be a 'real' bug, but one of those nice W3C-spec things).
   * 
   * Forget position b) now. It's just for info. Because the way we will solve a) will also solve b) too. 
   *
   * THE PROBLEM
   * To understand the problem, here a sample:
   * Given is the following XML:    "<AAA> &lt; &nbsp; &gt; </AAA>"
   *   Try to parse it and PHP's XML parser will fail with a XML_ERROR_UNDEFINED_ENTITY becaus of 
   *   the unknown litteral-entity '&nbsp;'. (The numeric equivalent '&#160;' would work though). 
   * Next try is to use the numeric equivalent 160 for '&nbsp;', thus  "<AAA> &lt; &#160; &gt; </AAA>"
   *   The data we receive in the tag <AAA> is  " <   > ". So we get the *translated entities* and 
   *   NOT the 3 entities &lt; &#160; &gt. Thus, we will not even notice that there were entities at all!
   *   In *most* cases we're not able to tell if the data was given as entity or as 'normal' char.
   *   E.g. When receiving a quote or a single space were not able to tell if it was given as 'normal' char
   *   or as &nbsp; or &quot;. Thus we loose the entity-information of the XML-data!
   * 
   * THE SOLUTION
   * The better solution is to keep the data 'as is' by replacing the '&' before parsing begins.
   * E.g. Taking the original input from above, this would result in "<AAA> &amp;lt; &amp;nbsp; &amp;gt; </AAA>"
   * The data we receive now for the tag <AAA> is  " &lt; &nbsp; &gt; ". and that's what we want.
   * 
   * The bad thing is, that a global replace will also replace data in section that are NOT translated by the 
   * PHP XML-parser. That is comments (<!-- -->), IP-sections (stuff between <? ? >) and CDATA-block too.
   * So all data comming from those sections must be reversed. This is done during the XML parse phase.
   * So:
   * a) Replacement of all '&' in the XML-source.
   * b) All data that is not char-data or in CDATA-block have to be reversed during the XML-parse phase.
   *
   */

-- 
Sam Blum <bs...@us...>

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