функция — PHP get_meta_tags () не работает, как я ожидал

Это потому что get_meta_tags ищет name приписывать.

Значение название собственность становится ключом

Все теги, которые вы ищете, перечислены под property приписывать.

Если вы являетесь владельцем исходной страницы, вы можете просто добавить name атрибут для элементов с тем же значением, что и property приписывать.

Если нет, то вы могли бы использовать что-то вроде DOMDocument в сочетании с file_get_contents или же curl чтобы получить конкретные значения, которые вас интересуют.

Например:

<?php
$content = file_get_contents('https://www.shoutmeloud.com/review-of-hostgator-webhosting-wordpress.html');

$doc = new DOMDocument();

// squelch HTML5 errors
@$doc->loadHTML($content);

$meta = $doc->getElementsByTagName('meta');
foreach ($meta as $element) {
$tag = [];
foreach ($element->attributes as $node) {
$tag[$node->name] = $node->value;
}
$tags []= $tag;
}

print_r($tags);

Результаты в:

Array
(
[0] => Array
(
[charset] => UTF-8
)

[1] => Array
(
[name] => viewport
[content] => width=device-width, initial-scale=1
)

[2] => Array
(
[name] => description
[content] => Check out HostGator review for year 2017. This review if written after using Hostgator for 5 years. Is Hostgator Good hosting? Find out answer here
)

[3] => Array
(
[property] => og:locale
[content] => en_US
)

[4] => Array
(
[property] => og:type
[content] => article
)

[5] => Array
(
[property] => og:title
[content] => A Blogger Review of HostGator Shared Hosting Plan
)

[6] => Array
(
[property] => og:description
[content] => Check out HostGator review for year 2017. This review if written after using Hostgator for 5 years. Is Hostgator Good hosting? Find out answer here
)

[7] => Array
(
[property] => og:url
[content] => https://www.shoutmeloud.com/review-of-hostgator-webhosting-wordpress.html
)

[8] => Array
(
[property] => og:site_name
[content] => ShoutMeLoud
)

[9] => Array
(
[property] => article:publisher
[content] => https://www.facebook.com/shoutmeloud
)

[10] => Array
(
[property] => article:author
[content] => https://www.facebook.com/denharsh
)

[11] => Array
(
[property] => article:tag
[content] => hostgator
)

[12] => Array
(
[property] => article:tag
[content] => Review
)

[13] => Array
(
[property] => article:tag
[content] => WordPress Webhosting
)

[14] => Array
(
[property] => article:section
[content] => Webhosting
)

[15] => Array
(
[property] => article:published_time
[content] => 2016-08-18T15:51:46+05:30
)

[16] => Array
(
[property] => article:modified_time
[content] => 2017-11-29T23:50:31+05:30
)

[17] => Array
(
[property] => og:updated_time
[content] => 2017-11-29T23:50:31+05:30
)

[18] => Array
(
[property] => fb:admins
[content] => 100000563323286
)

[19] => Array
(
[property] => og:image
[content] => https://www.shoutmeloud.com/wp-content/uploads/2014/08/Review-of-Hostgator-Shared-Hosting-Plan.jpg
)

[20] => Array
(
[property] => og:image:secure_url
[content] => https://www.shoutmeloud.com/wp-content/uploads/2014/08/Review-of-Hostgator-Shared-Hosting-Plan.jpg
)

[21] => Array
(
[name] => twitter:card
[content] => summary_large_image
)

[22] => Array
(
[name] => twitter:description
[content] => Check out HostGator review for year 2017. This review if written after using Hostgator for 5 years. Is Hostgator Good hosting? Find out answer here
)

[23] => Array
(
[name] => twitter:title
[content] => A Blogger Review of HostGator Shared Hosting Plan
)

[24] => Array
(
[name] => twitter:site
[content] => @shoutmeloud
)

[25] => Array
(
[name] => twitter:image
[content] => https://www.shoutmeloud.com/wp-content/uploads/2014/08/Review-of-Hostgator-Shared-Hosting-Plan.jpg
)

[26] => Array
(
[name] => twitter:creator
[content] => @denharsh
)

[27] => Array
(
[name] => generator
[content] => WordPress 4.9.1
)

[28] => Array
(
[name] => generator
[content] => Easy Digital Downloads v2.8.14
)

[29] => Array
(
[property] => fb:pages
[content] => 94019601674
)

[30] => Array
(
[name] => msapplication-TileImage
[content] => https://www.shoutmeloud.com/wp-content/uploads/2017/12/cropped-favicon-270x270.png
)

[31] => Array
(
[content] => Hostgator
[itemprop] => name
)

[32] => Array
(
[content] => 1
[itemprop] => worstRating
)

[33] => Array
(
[content] => 4.5
[itemprop] => ratingValue
)

[34] => Array
(
[content] => 5
[itemprop] => bestRating
)

[35] => Array
(
[content] => Hostgator
[itemprop] => name
)

)