apply_filters( ‘get_to_ping’, string[] $to_ping )

More Information

• Callback functions applied to this filter should not ping the URLs. Instead, they may modify the array of URLs to be pinged, and WordPress will ping them automatically.
• Note that each of the filter callback functions must return an array of URLs after it is finished processing. Otherwise, any code using the $to_ping array will break and other plugins also filtering the $to_ping array may generate errors.