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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.

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.

Attribute Name | Type | Required | Default | Description
--- | --- | --- | --- | ---
var | mixed | Yes | n/a | Variable (or string) to evaluate
assign | string | No | n/a | The template variable the output will be assigned to

> Technical 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 enabled, the output will be cached with the rest of the template.

Example 8-6. {eval} The contents of the config file, `setup.conf`.
    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:
    {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:
    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>.

Example 8-7. Another {eval} example This outputs the server name (in uppercase) and IP. The assigned variable `$str` could be from a database query.
`<?php $str = 'The server name is {$smarty.server.SERVER_NAME|upper} ' .'at {$smarty.server.SERVER_ADDR}'; $smarty->assign('foo',$str); ?>`
Where the template is:
    {eval var=$foo}

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