After switch to php 8.1 some warnings were catched in amp_node_view():
Deprecated function: preg_match_all(): Passing null to parameter #2 ($subject) of type string is deprecated in token_scan() (line 118 of .../docroot/includes/token.inc)
Deprecated function: strip_tags(): Passing null to parameter #1 ($string) of type string is deprecated in amp_node_view() (line 672 of .../modules/contrib/amp/amp.module).
Deprecated function: substr(): Passing null to parameter #1 ($string) of type string is deprecated in amp_node_view() (line 690 of .../modules/contrib/amp/amp.module).
Deprecated function: strip_tags(): Passing null to parameter #1 ($string) of type string is deprecated in {closure}() (line 739 of .../modules/contrib/amp/amp.module).
1. Enable php8.1.
2. Go to some amp page for any node.
3. Check logs.
The variable 'amp_metadata_options_' . $node->type is not set.
I suggest 2 options:
1) In addition to https://www.drupal.org/project/amp/issues/3198210 🐛 Edit Notice: Trying to access array offset on value of type null on php 7.4 and php8.1 Needs review make null variable conversion to string. Please see https://git.drupalcode.org/project/amp/-/merge_requests/14
2) Do not add AMP metadata for case, when the variable 'amp_metadata_options_' . $node->type is not set. Please see https://git.drupalcode.org/project/amp/-/merge_requests/15
Needs review
1.0
Code
The issue particularly affects sites running on PHP version 8.1.0 or later.