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# Introduction - template syntax

Introduction - template syntax -- Creating and editing templates

## Placeholders

The default format of placeholder is

    {[0-9A-Za-z_-]+}

This means, the name of the placeholder can consist of upper- and lowercase letters, underscores and hyphens. The name must be placed between curly brackets without any spaces.

Actual values for the placeholders are set using setVariable() and setGlobalVariable() methods. Placeholders for which no values were set are removed from output by default.

## Blocks

The format of a block is

    <!-- BEGIN [0-9A-Za-z_-]+ -->
    ... block content ...
    <!-- END [0-9A-Za-z_-]+ -->

The rules for the block name are the same like for placeholders. In contrast to placeholders the spaces in the block markup are required.

The nesting of blocks is permitted, but be careful while parsing. You have to parse() the innermost block first and then go from inner to outer.

In Sigma the whole template itself is treated as a virtual block called `"__global__"`. Most block-related functions use this block name as default.

## <!-- INCLUDE --> statements

It is possible to include a template file from within another template file using an `<!-- INCLUDE filename -->` statement:

    ... some content ...
    <!-- INCLUDE filename.html -->
    ... some more content ...

When such a template file gets loaded, the `<!-- INCLUDE filename.html -->` will be replaced by contents of `filename.html`.

Some things to note:

- Although this functionality is implemented using addBlockfile(), unlike addBlockfile() no new blocks are created in the template.

- `<!-- INCLUDE -->` calls are processed before any variable substitution can take place. So `<!-- INCLUDE {placeholder} -->` will not work unless you actually have a file named `{placeholder}` and want to load it.

## Template functions

Sigma templates can contain simple function calls. This means that the author of the template can add a special placeholder to it

    ... some content ...
    func_h1("embedded in h1")
    ... some more content ...

Sigma will parse the template for these placeholders and will allow you to define a callback function for them via setCallbackFunction(). Callback will be called automatically when the block containing such function call is parse()'d.

Format of such function name is as follows

    func_[_a-zA-Z]+[A-Za-z_0-9]*

that means that it should start with a 'func_' prefix, then has a letter or an undercore and then a sequence of letters, digits or underscores. Arguments to these template functions can contain variable placeholders

    func_translate('Hello, {username}')

but not blocks or other function calls.

### Quoting of template function arguments

> Note: The information in this section applies to HTML_Template_Sigma version 1.1.2 and later, please upgrade if you have problems with template function arguments in previous versions.

Quoting of function arguments is not mandatory, the following is a perfectly valid template function:

    func_uppercase(Some unquoted text)

But consider the following: function arguments are contained within parentheses and separated by commas. Therefore if closing parenthesis `')'` or comma `','` appears in function argument, it should be quoted.

The next thing to consider is that HTML_Template_Sigma is mostly targeted for generating HTML. Therefore a quoted string within an argument is most probably a tag attribute. The contents of such strings are not parsed for commas and parentheses. Therefore the following is also a perfectly valid template function:

    func_foo(<a href="javascript:foo(bar, baz)">Do foo</a>)

But if you have an unmatched single or double quote in your argument or if the argument starts with a quote, it should be quoted.

Finally, the argument should be quoted if it is an empty string or if its leading or trailing whitespace is significant (leading and trailing whitespace will be removed from unquoted arguments).

The arguments can be quoted using either single or double quotes. If an argument contains a quote of the same type, then it should be escaped using the backslash symbol `'\'`. The backslash symbol itself should also be escaped,

    func_foo('O\'really')
    func_foo('AC\\DC')

will pass `O'really` and `AC\DC` to the relevant callbacks.

Example 41-1. Valid and invalid template function arguments
    Valid arguments:
    func_foo(Some unquoted text)
    func_foo("Some quoted text")
    func_foo(<a href="javascript:foo(bar, baz)">Do foo</a>)
    func_foo('O\'really')
    func_foo('AC\\DC')

    Invalid arguments:
    func_foo(Hello, {username}) contains a comma, will yield two arguments instead of one
    func_foo(O'really) unmatched single quote
    func_foo('O'really') unescaped single quote
    func_foo(, 'whatever') empty arguments should be quoted

## Shorthand for template functions

Since release 1.1.0, instead of using

    func_callback({var})

you can write

    {var:callback}

There are 3 automatically registered template functions

- 'h' for htmlspecialchars()

- 'u' for urlencode()

- 'j' for a method of Sigma that escapes the string for usage in Javascript string constants.

Thus, if you add `{var:h}` placeholder to the template, var will be have unsafe characters replaced by corresponding HTML entitites.

## Usage Example

> Other usage examples: There are several usage examples in the package archive that cover most of its functionality. You are encouraged to review them along with the docs.

Example 41-2. The `table.html` template file
    <html>
    <body>
    <table cellpadding="2" cellspacing="0" border="1">
    <!-- INCLUDE table_header.html -->
    <!-- BEGIN table_row -->
        <tr>
            <td bgcolor="func_bgcolor('#CCCCCC', '#F0F0F0')">{first_name}</td>
            <td bgcolor="func_bgcolor('#CCCCCC', '#F0F0F0')">{last_name}</td>
        </tr>
    <!-- END table_row -->
    </table>
    </body>
    </acronym>

Example 41-3. The `table_header.html` template file
    <tr>
            <th>First name</th>
            <th>Last name</th>
        </tr>

Example 41-4. The script
    <?php

    require_once 'HTML/Template/Sigma.php';

    function toggle($item1, $item2)
    {
        static $i = 1;

        return $i++ % 2? $item1: $item2;
    }

    $data = array (
        array("Stig", "Bakken"),
        array("Martin", "Jansen"),
        array("Alexander", "Merz")
    );

    $tpl =& new HTML_Template_Sigma('.');

    $tpl->loadTemplateFile('table.html');

    $tpl->setCallbackFunction('bgcolor', 'toggle');

    foreach ($data as $name) {
        // assign data
        $tpl->setVariable(array(
            'first_name'  => $name[0],
            'last_name' => $name[1]
        ));
        // process the block
        $tpl->parse('table_row');
    }

    // print out the output
    $tpl->show();
    ?>

Example 41-5. The output
    <html>
    <body>
    <table cellpadding="2" cellspacing="0" border="1">
        <tr>
            <th>First name</th>
            <th>Last name</th>
        </tr>

        <tr>
            <td bgcolor="#CCCCCC">Stig</td>
            <td bgcolor="#CCCCCC">Bakken</td>
        </tr>

        <tr>
            <td bgcolor="#F0F0F0">Martin</td>
            <td bgcolor="#F0F0F0">Jansen</td>
        </tr>

        <tr>
            <td bgcolor="#CCCCCC">Alexander</td>
            <td bgcolor="#CCCCCC">Merz</td>
        </tr>

    </table>
    </body>
    </html>

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