Log¶
Log has several meanings:
Log file, or logging, to collect events traces as they happen
Logarithm, the math function
As a logging mechanism, PHP provides the low-level error_log() function to write a message to the system logger, a file, or by email, and the log_errors/error_log php.ini directives to route uncaught errors there automatically. Above that layer, PSR-3 Psr\Log\LoggerInterface standardizes a common logging API across eight severity levels, from debug to emergency, and Monolog is the de facto implementation used by Symfony, Laravel, and most modern frameworks, dispatching log records to handlers such as files, syslog, Slack, Sentry, or Elasticsearch.
As a math function, log() computes the natural logarithm by default, or the logarithm to an arbitrary base when a second argument is supplied; log10() provides base-10 logarithms directly, but PHP has no dedicated base-2 function, so it is computed as log($x, 2).
Related : Logarithm, Log File, Monitoring, STDOUT, Telemetry, Troubleshoot