2023-04-09 23:51:23 +02:00

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# {eval}
`{eval}` is used to evaluate a variable as a template. This can be used
for things like embedding template tags/variables into variables or
tags/variables into config file variables.
## Attributes
| Attribute Name | Required | Description |
|----------------|----------|------------------------------------------------------|
| var | Yes | Variable (or string) to evaluate |
| assign | No | The template variable the output will be assigned to |
If you supply the `assign` attribute, the output of the `{eval}`
function will be assigned to this template variable instead of being
output to the template.
> **Note**
>
> - Evaluated variables are treated the same as templates. They follow
> the same escapement and security features just as if they were
> templates.
>
> - Evaluated variables are compiled on every invocation, the compiled
> versions are not saved! However, if you have [caching](../../programmers/caching.md)
> enabled, the output will be cached with the rest of the template.
>
> - If the content to evaluate doesn't change often, or is used
> repeatedly, consider using
> `{include file="string:{$template_code}"}` instead. This may cache
> the compiled state and thus doesn't have to run the (comparably
> slow) compiler on every invocation.
## Examples
The contents of the config file, `setup.conf`.
```ini
emphstart = <strong>
emphend = </strong>
title = Welcome to {$company}'s home page!
ErrorCity = You must supply a {#emphstart#}city{#emphend#}.
ErrorState = You must supply a {#emphstart#}state{#emphend#}.
```
Where the template is:
```smarty
{config_load file='setup.conf'}
{eval var=$foo}
{eval var=#title#}
{eval var=#ErrorCity#}
{eval var=#ErrorState# assign='state_error'}
{$state_error}
```
The above template will output:
```html
This is the contents of foo.
Welcome to Foobar Pub & Grill's home page!
You must supply a <strong>city</strong>.
You must supply a <strong>state</strong>.
```
This outputs the server name (in uppercase) and IP. The assigned
variable `$str` could be from a database query.
```php
<?php
$str = 'The server name is {$smarty.server.SERVER_NAME|upper} '
.'at {$smarty.server.SERVER_ADDR}';
$smarty->assign('foo',$str);
```
Where the template is:
```smarty
{eval var=$foo}
```