CODEWITHSUNDEEP
php
Max Koretskyi
Max Koretskyi

Reputation: 105497

what is the possibility of not unique id in a loop

I'm looping through an array and for each record generating unique identifier with uniqid:

foreach($emailsByCampaign as $campaign => $emails) {
    $campaignHex = $this->strToHex($campaign);
    $values = "(";
    for ($i=0; $i<sizeof($emails);$i++) {
        $values .= $analyticsDbInstance->escape($emails[$i]) . ",'" . uniqid(true) . "'), (";
    }
}

Official documentation states that uniqid generates id based on microseconds. What is the likely that two cycles of the loop will pass in less than two seconds which will lead to not unique ids?

Upvotes: 4

Views: 978

Answers (1)

user1864610
user1864610

Reputation:

uniqid() generates a value based on the number of microseconds since the start of the Unix epoch - 1st January 1970. On a single machine every ID will be unique. It is possible (but unlikely) that two separate machines might generate the same uniqid() in which case the prefix and entropy parameters can be used to avoid this.

There are a number of implementations of UUID (or GUID) in PHP, but these generally generate V4 UUIDs, which aren't guaranteed to be unique (but the probability of a collision is vanishingly small)

If you need to generate something more secure you can use openssl-random-pseudo-bytes()

Upvotes: 4

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