Adds backslashes before letters and before a number at the start of a string.
Searches content for shortcodes and filter shortcodes through their hooks.
Calls the callback functions that have been added to a filter hook, specifying arguments in an array.
The `apply_filters_deprecated()` function in WordPress triggers a deprecation notice and fires the original filter hook when a filter hook is deprecated
Calls the callback functions that have been added to a filter hook.
Converts email addresses characters to HTML entities to block spam bots.
Determines whether the specified module exist in the Apache config.
The `allow_subdomain_install()` function in WordPress determines if subdomain installations are allowed on a Multisite network
The `allow_subdirectory_install()` function in WordPress allows users to determine if a subdirectory installation is permitted in a Multisite network setup