user_guide_src/source/libraries/parser.rst
#####################
Template Parser Class
#####################
The Template Parser Class can perform simple text substitution for
pseudo-variables contained within your view files.
It can parse simple variables or variable tag pairs.
If you've never used a template engine,
pseudo-variable names are enclosed in braces, like this::
<html lang="en">
<head>
<title>{blog_title}</title>
</head>
<body>
<h3>{blog_heading}</h3>
{blog_entries}
<h5>{title}</h5>
<p>{body}</p>
{/blog_entries}
</body>
</html>
These variables are not actual PHP variables, but rather plain text
representations that allow you to eliminate PHP from your templates
(view files).
.. note:: CodeIgniter does **not** require you to use this class since
using pure PHP in your view pages lets them run a little faster.
However, some developers prefer to use a template engine if
they work with designers who they feel would find some
confusion working with PHP.
.. important:: The Template Parser Class is **not** a full-blown
template parsing solution. We've kept it very lean on purpose in order
to maintain maximum performance.
.. contents::
:local:
.. raw:: html
<div class="custom-index container"></div>
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Using the Template Parser Class
*******************************
Initializing the Class
======================
Like most other classes in CodeIgniter, the Parser class is initialized
in your controller using the ``$this->load->library()`` method::
$this->load->library('parser');
Once loaded, the Parser library object will be available using:
$this->parser
Parsing templates
=================
You can use the ``parse()`` method to parse (or render) simple templates,
like this::
$data = array(
'blog_title' => 'My Blog Title',
'blog_heading' => 'My Blog Heading'
);
$this->parser->parse('blog_template', $data);
The first parameter contains the name of the :doc:`view
file <../general/views>` (in this example the file would be called
blog_template.php), and the second parameter contains an associative
array of data to be replaced in the template. In the above example, the
template would contain two variables: {blog_title} and {blog_heading}
There is no need to "echo" or do something with the data returned by
$this->parser->parse(). It is automatically passed to the output class
to be sent to the browser. However, if you do want the data returned
instead of sent to the output class you can pass TRUE (boolean) as the
third parameter::
$string = $this->parser->parse('blog_template', $data, TRUE);
Variable Pairs
==============
The above example code allows simple variables to be replaced. What if
you would like an entire block of variables to be repeated, with each
iteration containing new values? Consider the template example we showed
at the top of the page::
<html lang="en">
<head>
<title>{blog_title}</title>
</head>
<body>
<h3>{blog_heading}</h3>
{blog_entries}
<h5>{title}</h5>
<p>{body}</p>
{/blog_entries}
</body>
</html>
In the above code you'll notice a pair of variables: {blog_entries}
data... {/blog_entries}. In a case like this, the entire chunk of data
between these pairs would be repeated multiple times, corresponding to
the number of rows in the "blog_entries" element of the parameters array.
Parsing variable pairs is done using the identical code shown above to
parse single variables, except, you will add a multi-dimensional array
corresponding to your variable pair data. Consider this example::
$this->load->library('parser');
$data = array(
'blog_title' => 'My Blog Title',
'blog_heading' => 'My Blog Heading',
'blog_entries' => array(
array('title' => 'Title 1', 'body' => 'Body 1'),
array('title' => 'Title 2', 'body' => 'Body 2'),
array('title' => 'Title 3', 'body' => 'Body 3'),
array('title' => 'Title 4', 'body' => 'Body 4'),
array('title' => 'Title 5', 'body' => 'Body 5')
)
);
$this->parser->parse('blog_template', $data);
If your "pair" data is coming from a database result, which is already a
multi-dimensional array, you can simply use the database ``result_array()``
method::
$query = $this->db->query("SELECT * FROM blog");
$this->load->library('parser');
$data = array(
'blog_title' => 'My Blog Title',
'blog_heading' => 'My Blog Heading',
'blog_entries' => $query->result_array()
);
$this->parser->parse('blog_template', $data);
Usage Notes
===========
If you include substitution parameters that are not referenced in your
template, they are ignored::
$template = 'Hello, {firstname} {lastname}';
$data = array(
'title' => 'Mr',
'firstname' => 'John',
'lastname' => 'Doe'
);
$this->parser->parse_string($template, $data);
// Result: Hello, John Doe
If you do not include a substitution parameter that is referenced in your
template, the original pseudo-variable is shown in the result::
$template = 'Hello, {firstname} {initials} {lastname}';
$data = array(
'title' => 'Mr',
'firstname' => 'John',
'lastname' => 'Doe'
);
$this->parser->parse_string($template, $data);
// Result: Hello, John {initials} Doe
If you provide a string substitution parameter when an array is expected,
i.e. for a variable pair, the substitution is done for the opening variable
pair tag, but the closing variable pair tag is not rendered properly::
$template = 'Hello, {firstname} {lastname} ({degrees}{degree} {/degrees})';
$data = array(
'degrees' => 'Mr',
'firstname' => 'John',
'lastname' => 'Doe',
'titles' => array(
array('degree' => 'BSc'),
array('degree' => 'PhD')
)
);
$this->parser->parse_string($template, $data);
// Result: Hello, John Doe (Mr{degree} {/degrees})
If you name one of your individual substitution parameters the same as one
used inside a variable pair, the results may not be as expected::
$template = 'Hello, {firstname} {lastname} ({degrees}{degree} {/degrees})';
$data = array(
'degree' => 'Mr',
'firstname' => 'John',
'lastname' => 'Doe',
'degrees' => array(
array('degree' => 'BSc'),
array('degree' => 'PhD')
)
);
$this->parser->parse_string($template, $data);
// Result: Hello, John Doe (Mr Mr )
View Fragments
==============
You do not have to use variable pairs to get the effect of iteration in
your views. It is possible to use a view fragment for what would be inside
a variable pair, and to control the iteration in your controller instead
of in the view.
An example with the iteration controlled in the view::
$template = '<ul>{menuitems}
<li><a href="{link}">{title}</a></li>
{/menuitems}</ul>';
$data = array(
'menuitems' => array(
array('title' => 'First Link', 'link' => '/first'),
array('title' => 'Second Link', 'link' => '/second'),
)
);
$this->parser->parse_string($template, $data);
Result::
<ul>
<li><a href="/first">First Link</a></li>
<li><a href="/second">Second Link</a></li>
</ul>
An example with the iteration controlled in the controller,
using a view fragment::
$temp = '';
$template1 = '<li><a href="{link}">{title}</a></li>';
$data1 = array(
array('title' => 'First Link', 'link' => '/first'),
array('title' => 'Second Link', 'link' => '/second'),
);
foreach ($data1 as $menuitem)
{
$temp .= $this->parser->parse_string($template1, $menuitem, TRUE);
}
$template = '<ul>{menuitems}</ul>';
$data = array(
'menuitems' => $temp
);
$this->parser->parse_string($template, $data);
Result::
<ul>
<li><a href="/first">First Link</a></li>
<li><a href="/second">Second Link</a></li>
</ul>
***************
Class Reference
***************
.. php:class:: CI_Parser
.. php:method:: parse($template, $data[, $return = FALSE])
:param string $template: Path to view file
:param array $data: Variable data
:param bool $return: Whether to only return the parsed template
:returns: Parsed template string
:rtype: string
Parses a template from the provided path and variables.
.. php:method:: parse_string($template, $data[, $return = FALSE])
:param string $template: Content to parse
:param array $data: Variable data
:param bool $return: Whether to only return the parsed template
:returns: Parsed template string
:rtype: string
This method works exactly like ``parse()``, only it accepts
the template as a string instead of loading a view file.
.. php:method:: set_delimiters([$l = '{'[, $r = '}']])
:param string $l: Left delimiter
:param string $r: Right delimiter
:rtype: void
Sets the delimiters (opening and closing) for a
pseudo-variable "tag" in a template.