function.math.php

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<?php
function smarty_function_math($params, &$smarty)
{
    // be sure equation parameter is present
    if (empty($params['equation'])) {
        $smarty->trigger_error("math: missing equation parameter");
        return;
    }

    // strip out backticks, not necessary for math
    $equation = str_replace('`','',$params['equation']);

    // make sure parenthesis are balanced
    if (substr_count($equation,"(") != substr_count($equation,")")) {
        $smarty->trigger_error("math: unbalanced parenthesis");
        return;
    }

    // match all vars in equation, make sure all are passed
    preg_match_all("!(?:0x[a-fA-F0-9]+)|([a-zA-Z][a-zA-Z0-9_]*)!",$equation, $match);
    $allowed_funcs = array('int','abs','ceil','cos','exp','floor','log','log10',
                           'max','min','pi','pow','rand','round','sin','sqrt','srand','tan');
    
    foreach($match[1] as $curr_var) {
        if ($curr_var && !in_array($curr_var, array_keys($params)) && !in_array($curr_var, $allowed_funcs)) {
            $smarty->trigger_error("math: function call $curr_var not allowed");
            return;
        }
    }

    foreach($params as $key => $val) {
        if ($key != "equation" && $key != "format" && $key != "assign") {
            // make sure value is not empty
            if (strlen($val)==0) {
                $smarty->trigger_error("math: parameter $key is empty");
                return;
            }
            if (!is_numeric($val)) {
                $smarty->trigger_error("math: parameter $key: is not numeric");
                return;
            }
            $equation = preg_replace("/\b$key\b/", " \$params['$key'] ", $equation);
        }
    }

    eval("\$smarty_math_result = ".$equation.";");

    if (empty($params['format'])) {
        if (empty($params['assign'])) {
            return $smarty_math_result;
        } else {
            $smarty->assign($params['assign'],$smarty_math_result);
        }
    } else {
        if (empty($params['assign'])){
            printf($params['format'],$smarty_math_result);
        } else {
            $smarty->assign($params['assign'],sprintf($params['format'],$smarty_math_result));
        }
    }
}

/* vim: set expandtab: */

?>