wp-optimize / webp / class-wpo-webp-alter-html.php

class-wpo-webp-alter-html.php in WP-Optimize – Cache, Compress images, Minify & Clean database to boost page speed & performance 3.7.0, at webp/class-wpo-webp-alter-html.php

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1	<?php
2
3	if (!defined('WPO_VERSION')) die('No direct access allowed');
4
5	if (!class_exists('WPO_WebP_Alter_HTML')) :
6
7	class WPO_WebP_Alter_HTML {
8
9	private $tags = array('img', 'source', 'input', 'iframe', 'div', 'li', 'link', 'a', 'section', 'video');
10
11	/**
12	* Constructor
13	*/
14	private function __construct() {
15	add_action('template_redirect', array($this, 'start'), 9999);
16	}
17
18	/**
19	* Returns singleton instance
20	*
21	* @return WPO_WebP_Alter_HTML
22	*/
23	public static function get_instance() {
24	static $_instance = null;
25	if (null === $_instance) {
26	$_instance = new self();
27	}
28	return $_instance;
29	}
30
31	/**
32	* Start to alter html in output buffer
33	*/
34	public function start() {
35	if (apply_filters('wpo_disable_webp_alter_html', false)) {
36	return;
37	}
38
39	if (!is_admin() \|\| (defined('DOING_AJAX') && DOING_AJAX)) {
40	ob_start(array(__CLASS__, 'alter_html'));
41	}
42	}
43
44	/**
45	* Alter html to change image related tags to specify webp images
46	*
47	* @param string $html - HTML document as string
48	* @return string
49	*/
50	public function alter_html($html) {
51
52	if (!WP_Optimize_Utils::is_valid_html($html)) return $html;
53
54	// MAX_FILE_SIZE is defined in simple_html_dom.
55	// For safety, we make sure it is defined before using
56	defined('MAX_FILE_SIZE') \|\| define('MAX_FILE_SIZE', 600000);
57
58	$dom = WP_Optimize_Utils::get_simple_html_dom_object($html);
59
60	if (false === $dom) {
61	if (strlen($html) > MAX_FILE_SIZE) {
62	return $html . "\n" . "<!-- Alter HTML was skipped because the HTML is too big to process! " .
63	"(limit is set to " . MAX_FILE_SIZE . " bytes) -->";
64	}
65	return $html . "\n" . "<!-- Alter HTML was skipped because the helper library refused to process the html -->";
66	}
67
68	// Replace attributes (src, srcset, data-src, etc)
69	foreach ($this->tags as $tag) {
70	$elems = $dom->find($tag);
71	foreach ($elems as $elem) {
72	$attributes = $elem->getAllAttributes();
73	foreach ($attributes as $attr_name => $attr_value) {
74	if ($this->is_image_attribute($attr_name)) {
75	$elem->setAttribute($attr_name, $this->handle_attribute($attr_value));
76	}
77	}
78	}
79	}
80
81	return $dom->save();
82	}
83
84	/**
85	* Append image urls with `.webp` extension
86	*
87	* @param strinng $url - Image URL
88	* @return string
89	*/
90	private function replace_url($url) {
91	return $url . '.webp';
92	}
93
94	/**
95	* If webp version for supplied image url is available then replace extension
96	*
97	* @param string $url - URL of image
98	* @return string
99	*/
100	private function maybe_replace_url($url) {
101	if ($this->is_webp_version_available($url)) {
102	$url = $this->replace_url($url);
103	}
104	return $url;
105	}
106
107	/**
108	* Modifies src attribute value, if needed
109	*
110	* @param string $attr_value
111	* @return string
112	*/
113	private function handle_src($attr_value) {
114	return $this->maybe_replace_url($attr_value);
115	}
116
117	/**
118	* Modified `srcset` attribute value, if needed
119	*
120	* @param string $attr_value
121	* @return string
122	*/
123	private function handle_srcset($attr_value) {
124	// $attr_value is ie: <img data-x="1.jpg 1000w, 2.jpg">
125	$srcset_arr = explode(',', $attr_value);
126	foreach ($srcset_arr as $i => $srcset_entry) {
127	// $srcset_entry is ie "image.jpg 520w", but can also lack width, ie just "image.jpg"
128	// it can also be ie "image.jpg 2x"
129	$srcset_entry = trim($srcset_entry);
130	$entry_parts = preg_split('/\s+/', $srcset_entry, 2);
131	if (count($entry_parts) == 2) {
132	list($src, $descriptors) = $entry_parts;
133	} else {
134	$src = $srcset_entry;
135	$descriptors = null;
136	}
137
138	$url = $this->maybe_replace_url($src);
139	$srcset_arr[$i] = $url . (isset($descriptors) ? ' ' . $descriptors : '');
140	}
141	return implode(', ', $srcset_arr);
142	}
143
144	/**
145	* Decides whether given value is a `srcset` or not
146	*
147	* @return bool
148	*/
149	private function looks_like_srcset($value) {
150	if (preg_match('#\s\d*(w\|x)#', $value)) {
151	return true;
152	}
153	return false;
154	}
155
156	/**
157	* Handle attribute value based on attribute name, src or srcset
158	*
159	* @return string
160	*/
161	private function handle_attribute($value) {
162	if ($this->looks_like_srcset($value)) {
163	return $this->handle_srcset($value);
164	}
165	return $this->handle_src($value);
166	}
167
168	/**
169	* Decide whether given attribute name is an image attribute or not
170	*
171	* @return bool
172	*/
173	private function is_image_attribute($attr_name) {
174	return preg_match('#^(src\|srcset\|poster\|(data-[^=](lazy\|small\|slide\|img\|large\|src\|thumb\|source\|set\|bg-url)[^=]))$#i', $attr_name);
175	}
176
177	/**
178	* Does webp image file exists
179	*
180	* @param string $url
181	* @return boolean
182	*/
183	private function is_webp_version_available($url) {
184	$filename = WP_Optimize_Utils::get_file_path($url);
185	if (empty($filename)) return false;
186	return file_exists($filename . '.webp');
187	}
188	}
189
190	endif;
191