2021-12-03 11:59:22 +01:00
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Template Inheritance {#advanced.features.template.inheritance}
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====================
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Inheritance brings the concept of Object Oriented Programming to
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templates, allowing you to define one (or more) base templates that can
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be extended by child templates. Extending means that the child template
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can override all or some of the parent named block areas.
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- The inheritance tree can be as deep as you want, meaning you can
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extend a file that extends another one that extends another one and
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so on.
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- The child templates can not define any content besides what\'s
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inside [`{block}`](#language.function.block) tags they override.
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Anything outside of [`{block}`](#language.function.block) tags will
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be removed.
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- The content of [`{block}`](#language.function.block) tags from child
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and parent templates can be merged by the `append` or `prepend`
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[`{block}`](#language.function.block) tag option flags and
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`{$smarty.block.parent}` or `{$smarty.block.child}` placeholders.
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- Template inheritance is a compile time process which creates a
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single compiled template file. Compared to corresponding solutions
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based on subtemplates included with the
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[`{include}`](#language.function.include) tag it does have much
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better performance when rendering.
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- The child template extends its parent defined with the
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[`{extends}`](#language.function.extends) tag, which must be the
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first line in the child template. Instead of using the
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[`{extends}`](#language.function.extends) tags in the template files
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you can define the whole template inheritance tree in the PHP script
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when you are calling [`fetch()`](#api.fetch) or
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[`display()`](#api.display) with the `extends:` template resource
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2022-10-22 22:08:38 +02:00
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type. The later provides even more flexibility.
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2021-12-03 11:59:22 +01:00
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> **Note**
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>
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> When `$compile_check` is enabled, all files in the inheritance tree
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> are checked for modifications upon each invocation. You may want to
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> disable `$compile_check` on production servers for this reason.
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> **Note**
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>
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> If you have a subtemplate which is included with
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> [`{include}`](#language.function.include) and it contains
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> [`{block}`](#language.function.block) areas it works only if the
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> [`{include}`](#language.function.include) itself is called from within
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> a surrounding [`{block}`](#language.function.block). In the final
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> parent template you may need a dummy
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> [`{block}`](#language.function.block) for it.
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layout.tpl (parent)
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<html>
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<head>
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<title>{block name=title}Default Page Title{/block}</title>
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{block name=head}{/block}
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</head>
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<body>
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{block name=body}{/block}
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</body>
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</html>
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myproject.tpl (child)
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{extends file='layout.tpl'}
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{block name=head}
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<link href="/css/mypage.css" rel="stylesheet" type="text/css"/>
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<script src="/js/mypage.js"></script>
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{/block}
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mypage.tpl (grandchild)
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{extends file='myproject.tpl'}
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{block name=title}My Page Title{/block}
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{block name=head}
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<link href="/css/mypage.css" rel="stylesheet" type="text/css"/>
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<script src="/js/mypage.js"></script>
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{/block}
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{block name=body}My HTML Page Body goes here{/block}
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To render the above use
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$smarty->display('mypage.tpl');
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The resulting output is
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<html>
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<head>
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<title>My Page Title</title>
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<link href="/css/mypage.css" rel="stylesheet" type="text/css"/>
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<script src="/js/mypage.js"></script>
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</head>
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<body>
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My HTML Page Body goes here
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</body>
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</html>
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Instead of using [`{extends}`](#language.function.extends) tags in the
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template files you can define the inheritance tree in your PHP script by
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using the [`extends:` resource](#resources.extends) type.
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The code below will return same result as the example above.
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<?php
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$smarty->display('extends:layout.tpl|myproject.tpl|mypage.tpl');
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?>
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See also [`{block}`](#language.function.block),
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[`{extends}`](#language.function.extends) and [`extends:`
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resource](#resources.extends)
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