Kind of automatic escaping in Smarty

compiler.end_context.php

<?php

function smarty_compiler_end_context($_, Smarty_Compiler $compiler)
{
    array_shift($compiler->default_modifiers);
}

compiler.start_context.php

<?php

function smarty_compiler_start_context($type, Smarty_Compiler $compiler)
{
    switch ($type) {
        case 'javascript':
            $modifier = 'escape:javascript';
            break;
        default:
            $compiler->trigger_error('Unknown context type ' . $type);
            return;
    }

    array_unshift($compiler->default_modifiers, $modifier);
}

main.php

<?php

$smarty = new Sugar_Smarty();
$smarty->default_modifiers = array('escape:\'html\':\'UTF-8\'');
$smarty->assign('var', '<script>
alert("xss");
</script>');
$smarty->display('test.tpl');

test.tpl

<div>Hey, this is {$var}</div>
<button data-var="{$var}" onclick="{start_context javascript}alert('{$var}'){end_context}">Click me, I'm {$var}</button>
<script>{start_context javascript}
    var name = "{$var}";
    alert(name);
{end_context}</script>