PHP end tag fails when used inside an attribute - is this a bug?

I am creating web content that may be included from various locations. For images I need to set the @src such that the image is always found, no matter where the web page might be. I am setting a $relpath in php - in the main page - to allow for this. I am using lots of php in my generated content and it works fine, except when I try to set the src attribute for an image.

Here is a very simple test file:

<?xml version="1.0" encoding="UTF-8"?> <image href="images/spaceship.png"></image>

I tried this transform:

<?xml version="1.0" encoding="UTF-8"?> <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:xs="http://www.w3.org/2001/XMLSchema" exclude-result-prefixes="xs" version="3.0"> <xsl:output method="html" encoding="UTF-8"/> <xsl:template match="/"> <xsl:apply-templates/> </xsl:template> <xsl:template match="image"> <img> <xsl:attribute name="src"> <xsl:processing-instruction name="php">echo $relpath</xsl:processing-instruction> <xsl:value-of select="@href"/> </xsl:attribute> </img> </xsl:template> </xsl:stylesheet>

This results in the following php file:

<img src="echo $relpathimages/spaceship.png">

Which obviously does not work. So I tried writing the php tags via xsl:text

<?xml version="1.0" encoding="UTF-8"?> <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:xs="http://www.w3.org/2001/XMLSchema" exclude-result-prefixes="xs" version="3.0"> <xsl:output method="html" encoding="UTF-8"/> <xsl:template match="/"> <xsl:apply-templates/> </xsl:template> <xsl:template match="image"> <img> <xsl:attribute name="src"> <xsl:text disable-output-escaping="yes">&lt;?php </xsl:text> <xsl:text>echo $relpath</xsl:text> <xsl:text disable-output-escaping="yes">?&gt;</xsl:text> <xsl:value-of select="@href"/> </xsl:attribute> </img> </xsl:template> </xsl:stylesheet>

This makes the php start tag appear correctly, but disabling the output escaping on the end tag is completely ignored by the XSL processor. I know I do not need to use > for the closing bracket but the same result appears when replacing it with '>'.

<img src="<?php echo $relpath?&gt;images/spaceship.png">

The required output is this:

<img src="<?php echo $relpath?>images/spaceship.png">

If there is another way of doing this let me know.