Reassess the required PHP extensions

[Cybr]

For the list of ​https://make.wordpress.org/hosting/handbook/handbook/server-environment/#php-extensions, I suggest these extensions to be listed:

• Required:
  • iconv (/wp-mail.php, wp-includes/formatting.php, SimplePie, etc. uses this)
  • mbstring (performance, stability: see #34631 to learn that not every mb_*() function has a fallback in WP)
  • zip (plugin unpacking, see wp-admin/file.php)

• Recommended:
  • opcache (performance, needs no introduction)

These changes should also affect the Site Health component brought in WordPress 5.2.

[fierevere]

Please note, on PHP 5.6 xcache or APC can be used instead of opcache, WinCache can be used on Windows platform. SiteHealth shoulnt produce a warning if alternate PHP opcode cacher is present.

[Cybr]

In ​https://make.wordpress.org/hosting/2019/06/11/php-requirements-check-in/:
The list on w.org is updated and now includes the required extensions listed above.

[desrosj]

Moving Site Health tickets into their lovely new home, the Site Health component.

[Clorith]

The required extensions were added to the Site Health checks in r46268, so closing out this ticket as worksforme at this time.