master/output_2icon_8php_source.html

 <?php
 $vars['class'] = elgg_extract_class($vars, ['elgg-icon']);

 echo elgg_format_element('span', $vars);
$vars
$vars['class']
Display an icon from the FontAwesome library.
Definition: icon.php:8

elgg_format_element
elgg_format_element(string $tag_name, array $attributes=[], string $text= '', array $options=[])
Format an HTML element.
Definition: output.php:145

elgg_extract_class
elgg_extract_class(array $array, array|string $existing=[], string $extract_key= 'class')
Extract class names from an array, optionally merging into a preexisting set.
Definition: elgglib.php:279