But I use Symphony CMS and can only use xslt 1.0

With XSLT 1.0 you can use
  <xsl:with-param name="foo">
    <xsl:choose>
      <xsl:when test="condition goes here">value goes here</xsl:when>
      <xsl:otherwise>other value goes here</xsl:when>
    </xsl:choose>
  </xsl:with-param>

	Martin Honnen --- MVP Data Platform Development
	http://msmvps.com/blogs/martin_honnen/