<xsl:template match="item" mode="basket">
...
</xsl:template>

Применение шаблона:

<xsl:apply-templates select="/page/data/coll/item" mode="basket"/>

<xsl:variable name="user_id">
    <xsl:choose>
        <xsl:when test="/page/user">
      <xsl:value-of select="/page/user/@id"/>
    </xsl:when>
        <xsl:when test="/ajx/search/user">
      <xsl:value-of select="/ajx/search/user/@id"/>
    </xsl:when>
        <xsl:otherwise>0</xsl:otherwise>
    </xsl:choose>
</xsl:variable>