Passing Variables into Layouts
Although we think of layouts being the same across multiple pages, there are usually small things that change from page to page. That might be the title in the HTML <title> tags, a class on the <body>, or whether to include a JavaScript file or not.
To help with this, we have layout variables. To use these you first need to define your variable in the page when you use the perch_layout() function, then you need to use the variable inside the layout.
Define the variable(s)
In the below code we have a global header Layout used on all pages of the website. This header includes the html title and body element. As we want to have unique titles on our pages and also add a class to the body to indicate a page or section of the site we can use Layotu Variables to pass this information into the header Layout.
When including the Layout on the page with the perch_layout() function, pass in a second argument after the name of the Layout. This argument is a PHP array, the key is the name of the variable and the value is what will be output when using this variable.
perch_layout('global.header', array(
'title'=>'Welcome to my site!',
'class'=>'home',
));
You can pass any value into the layout using an array.
Using a variable in a layout
As Layouts are PHP, you can use the variables passed into them in a variety of ways. The most simple use is to display the contents of the variable.
To use a variable in a layout, we have the perch_layout_var() function. The below code is inside our global.header.php layout file, and outputs the value of the title variable passed in from the array.
<title><?php perch_layout_var('title'); ?></title>
Values are automatically HTML-encoded so they’re safe for output. To return the value, or get it before it’s encoded (essential if the variable isn’t a string), add a second argument of true to the perch_layout_var() function. The below code would not directly output the value of title but instead write it to a PHP variable called $title.
<?php $title = perch_layout_var('title', true); ?>
Testing for a layout variable
You can test to see if a layout variable has been set using perch_layout_has(), passing in the name of the variable. In the below code we check to see if a variable named title has been set. If it has, we use it. If not we output a string.
<?php
if (perch_layout_has('title')) {
perch_layout_var('title');
}else{
echo "Welcome to my site!";
}
?>