Hi,
For WampServer the yaml is a PHP extension, so should be referenced with
a extension line in a php.ini file.
The yaml must be for the correct operating system, match the
PHP version, and for whether PHP is built as Thread-Safe (TS).
Important: respect the dll versions for php.
Download yaml for Windows php_yaml-2.1.0-7.4-ts-vc15-x64.zip (64 bits) or php_yaml-2.1.0-7.4-ts-vc15-x3
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WampServer English