htmlpurifier/library/HTMLPurifier/VarParser/Native.php

<?php

/**
 * This variable parser uses PHP's internal code engine. Because it does
 * this, it can represent all inputs; however, it is dangerous and cannot
 * be used by users.
 */
class HTMLPurifier_VarParser_Native extends HTMLPurifier_VarParser
{
    
    protected function parseImplementation($var, $type, $allow_null) {
        return $this->evalExpression($var);
    }
    
    protected function evalExpression($expr) {
        $var = null;
        $result = eval("\$var = $expr;");
        if ($result === false) {
            throw new HTMLPurifier_VarParserException("Fatal error in evaluated code");
        }
        return $var;
    }
    
}