PHP date plus minus

For daily Statistics, our date ("Ymd") is converted to integer as the primary key of the database, so it is necessary to use time to add and subtract when searching for a period of time statistic data;

For example, data within 30 days

function GetData ($writetime, $limit) {$start _unix = Strtotime ($start); for ($i = 0; $i < $limit; $i + +) {$writetime = dat E ("Ymd", $start _unix); _stdout ($writetime); $start _unix-= 3600 * 24;}}

About the visualization of the statistical database, we have been looking for ways to use the background calculation, filtering data, to get the statistics we want, but MySQL group by these operations is slow, I hope to get advice.

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