If you are installing the Drupal 8, you must have came across OPcode caching warning. Well to get rid of this warning follow below guide to install and enable OPcode caching on your local.
First, you have to locate "php_opcache.dll" file in your XAMPP instalation directory.
Then once you have located it(in my case it was at "C:\xampp\php\ext".
Now open php.ini file and find [opcache], just above that put below line,
zend_extension=php_opcache.dll ( for me it is "zend_extension=C:/xampp/php/ext/php_opcache.dll" )
Then uncomment "opcache.enable=0" line and change 0 to 1. (Remove semicolon(;) to uncomment)
Uncomment below opcache configurations as per your need.
Once done restart Apache server and click on "retry" at the bottom of the page requirements review page of Drupal 8.
And you will be redirected to the Database Configuration page.
Hope this works with you, if not please write me below in comment section.
My php.ini file for opcache looks something like below,
zend_extension=C:/xampp/php/ext/php_opcache.dll[opcache]; Determines if Zend OPCache is enabledopcache.enable=1; Determines if Zend OPCache is enabled for the CLI version of PHPopcache.enable_cli=0; The OPcache shared memory storage size.opcache.memory_consumption=64; The amount of memory for interned strings in Mbytes.opcache.interned_strings_buffer=4; The maximum number of keys (scripts) in the OPcache hash table.; Only numbers between 200 and 100000 are allowed.opcache.max_accelerated_files=2000; The maximum percentage of "wasted" memory until a restart is scheduled.opcache.max_wasted_percentage=5; When this directive is enabled, the OPcache appends the current working; directory to the script key, thus eliminating possible collisions between; files with the same name (basename). Disabling the directive improves; performance, but may break existing applications.opcache.use_cwd=1; When disabled, you must reset the OPcache manually or restart the; webserver for changes to the filesystem to take effect.;opcache.validate_timestamps=1; How often (in seconds) to check file timestamps for changes to the shared; memory storage allocation. ("1" means validate once per second, but only; once per request. "0" means always validate);opcache.revalidate_freq=2; Enables or disables file search in include_path optimization;opcache.revalidate_path=0; If disabled, all PHPDoc comments are dropped from the code to reduce the; size of the optimized code.;opcache.save_comments=1; If disabled, PHPDoc comments are not loaded from SHM, so "Doc Comments"; may be always stored (save_comments=1), but not loaded by applications; that don't need them anyway.;opcache.load_comments=1; If enabled, a fast shutdown sequence is used for the accelerated code;opcache.fast_shutdown=0; Allow file existence override (file_exists, etc.) performance feature.;opcache.enable_file_override=0; A bitmask, where each bit enables or disables the appropriate OPcache; passes;opcache.optimization_level=0xffffffff;opcache.inherited_hack=1;opcache.dups_fix=0; The location of the OPcache blacklist file (wildcards allowed).; Each OPcache blacklist file is a text file that holds the names of files; that should not be accelerated. The file format is to add each filename; to a new line. The filename may be a full path or just a file prefix; (i.e., /var/www/x blacklists all the files and directories in /var/www; that start with 'x'). Line starting with a ; are ignored (comments).;opcache.blacklist_filename=; Allows exclusion of large files from being cached. By default all files; are cached.;opcache.max_file_size=0; Check the cache checksum each N requests.; The default value of "0" means that the checks are disabled.;opcache.consistency_checks=0; How long to wait (in seconds) for a scheduled restart to begin if the cache; is not being accessed.;opcache.force_restart_timeout=180; OPcache error_log file name. Empty string assumes "stderr".;opcache.error_log=; All OPcache errors go to the Web server log.; By default, only fatal errors (level 0) or errors (level 1) are logged.; You can also enable warnings (level 2), info messages (level 3) or; debug messages (level 4).;opcache.log_verbosity_level=1; Preferred Shared Memory back-end. Leave empty and let the system decide.;opcache.preferred_memory_model=; Protect the shared memory from unexpected writing during script execution.; Useful for internal debugging only.;opcache.protect_memory=0