Description:
------------
I have been able to replicate under three environment running Ubuntu LTS php5 (cli, cgi or mod_php), libxslt 1.1.26 and the php5 module and librdf0 and the php5 module.

With the above setup, any <xsl:import href="local/file.xsl" /> call will fail with the error

XSLTProcessor::importStylesheet(): Local file read for /path/to/local/file.xsl refused

Using XSLCache will result in a segfault and no errors.

Removing php5's librdf module fixes the issue.

Test script:
---------------
# a.php 
<?php
ini_set('display_errors', 1);
ini_set('error_reporting', E_ALL|E_STRICT|E_NOTICE);

//phpinfo();

$doc = new DOMDocument();
$xsl = new XSLTProcessor();

$xsl_filename = __DIR__ . '/collection.xsl';
$xml_filename = __DIR__ . '/collection.xml';

$doc->load($xsl_filename);
$xsl->importStyleSheet($doc);

$doc->load($xml_filename);
echo $xsl->transformToXML($doc);

# collection.xml
<collection>
 <cd>
  <title>Fight for your mind</title>
  <artist>Ben Harper</artist>
  <year>1995</year>
 </cd>
 <cd>
  <title>Electric Ladyland</title>
  <artist>Jimi Hendrix</artist>
  <year>1997</year>
 </cd>
</collection>

# collection.xsl
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
 <xsl:import href="file:///var/www/pgadmin/temp/collection2.xsl" />
 <xsl:param name="owner" select="'Nicolas Eliaszewicz'"/>
 <xsl:output method="html" encoding="iso-8859-1" indent="no"/>
 <xsl:template match="collection">
  Hey! Welcome to <xsl:value-of select="$owner"/>'s sweet CD collection!
  <xsl:apply-templates/>
 </xsl:template>
 <xsl:template match="cd">
  <h1><xsl:value-of select="title"/></h1>
  <h2>by <xsl:value-of select="artist"/> - <xsl:value-of select="year"/></h2>
  <hr />
 </xsl:template>
</xsl:stylesheet>

# collection2.xsl
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
 <xsl:param name="owner" select="'Nicolas Eliaszewicz'"/>
 <xsl:output method="html" encoding="iso-8859-1" indent="no"/>
 <xsl:template match="collection">
  Hey! Welcome to <xsl:value-of select="$owner"/>'s sweet CD collection!
  <xsl:apply-templates/>
 </xsl:template>
 <xsl:template match="cd">
  <h1><xsl:value-of select="title"/></h1>
  <h2>by00 <xsl:value-of select="artist"/> - <xsl:value-of select="year"/></h2>
  <hr />
 </xsl:template>
</xsl:stylesheet>


Expected result:
----------------
A parsed XSLT document with the imported stylesheets. And no errors ;)

Actual result:
--------------
Warning: XSLTProcessor::importStylesheet(): error in /var/www/temp/a.php on line 14

Call Stack:
    0.0002     627304   1. {main}() /var/www/temp/a.php:0
    0.0006     631128   2. XSLTProcessor->importStylesheet() /var/www/temp/a.php:14


Warning: XSLTProcessor::importStylesheet(): Local file read for file:///var/www/pgadmin/temp/collection2.xsl refused in /var/www/temp/a.php on line 14

Call Stack:
    0.0002     627304   1. {main}() /var/www/temp/a.php:0
    0.0006     631128   2. XSLTProcessor->importStylesheet() /var/www/temp/a.php:14