Generate unique random numbers to be stored in database

Question

Below is my code to check if the generated random number is available in the database. If the $smsCode is already in the database, then generate a new random number. But it is not working as expected.

$smsCode = 7552; $query = "SELECT * FROM appointment WHERE sms_code = '$smsCode'"; while($conn->query($query) === TRUE){ $smsCode = rand(1000,9999); $query = "SELECT * FROM appointment WHERE sms_code = '$smsCode'"; $conn->query($query); } $sql = "INSERT INTO appointment(number) VALUES('$smsCode');

$smsCode = 7552 is already in the database but it keeps storing 7552 into the database instead of generating a new number to be stored in the database.

Manikiran · Accepted Answer · 2015-10-18 06:05:16Z

<?php $sms_code=rand(1000,9999); $cond=True; while($cond){ $query = "SELECT * FROM appointment WHERE sms_code = '$smsCode'"; $result = $conn->query($query); if(mysql_num_rows($result)>0) { $sms_code=rand(1000,9999); } else { $cond=False; } } $sql = "INSERT INTO appointment(number) VALUES('$smsCode')"; ?>

bish · Accepted Answer · 2015-10-18 07:00:50Z

If the result of your first query returns a valid result it doesn't return true. The query() function only returns false if it fails, see PHP manual. So the condition of your while-loop where you make a comparison to the boolean true (cause of strict type comparions with three =) will never be true and so no new value is assigned to $smsCode.

Try something like this

$smsCode = 7552; while(true) { $query = "SELECT * FROM appointment WHERE sms_code = '$smsCode'"; if($conn->query($query) === false) { $sql = "INSERT INTO appointment(number) VALUES('$smsCode')"; break; } else { $smsCode = rand(1000,9999); } }

This should generate a new code every time you don't have row in your database with that code.

You need to place it before ;, but anyways, its more efficient than my code :)
A do { ... } while () would be more sensible syntax. BUT this approach is NOT "race condition" safe.

Shaymol Bapary · Accepted Answer · 2015-10-18 07:10:28Z

you can try this

$date = date_create(); $smsCode = date_timestamp_get($date);

each time it will give you an unique random numbers

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