gnu-social/vendor/ezyang/htmlpurifier/library/HTMLPurifier/AttrTransform/Background.php

<?php

/**
 * Pre-transform that changes proprietary background attribute to CSS.
 */
class HTMLPurifier_AttrTransform_Background extends HTMLPurifier_AttrTransform
{
    /**
     * @param array $attr
     * @param HTMLPurifier_Config $config
     * @param HTMLPurifier_Context $context
     * @return array
     */
    public function transform($attr, $config, $context)
    {
        if (!isset($attr['background'])) {
            return $attr;
        }

        $background = $this->confiscateAttr($attr, 'background');
        // some validation should happen here

        $this->prependCSS($attr, "background-image:url($background);");
        return $attr;
    }
}

// vim: et sw=4 sts=4