How to auto generate unique id in php?

How to Generate a Unique ID in PHP

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Updated on October 02, 2018

A unique user ID can be created in PHP using the uniqid () function. This function has two parameters you can set.

The first is the prefix, which is what will be appended to the beginning of each ID. The second is more_entropy. If this is false or not specified, it will return 13 characters; if it's true, 23 characters will be returned.

Examples For Creating a Unique ID

Below are examples of creating a unique user ID, but each are a little different.

The first creates a normal unique ID while the second shows how to make a longer ID. The third example creates an ID with a random number as the prefix while the last line can be used to encrypt the username before storing it.

//creates a unique id with the 'about' prefix $a = uniqid(about); echo $a; echo "
";

//creates a longer unique id with the 'about' prefix $b = uniqid (about, true); Echo $b; echo "
";

//creates a unique ID with a random number as a prefix - more secure than a static prefix $c = uniqid (rand (),true); echo $c; echo "
";

//this md5 encrypts the username from above, so its ready to be stored in your database $md5c = md5($c); echo $md5c; ?>

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The uniqid() function in PHP is an inbuilt function which is used to generate a unique ID based on the current time in microseconds (micro time). 
The ID generated from the uniqid() function is not optimal since it is based on the system time and is not cryptographically secured. Thus it should not be for cryptographical purposes.
The uniqid( ) function accepts prefix and more_entropy as parameters and returns timestamp based unique identifier as a string.
 

Syntax:  

 uniqid($prefix, $more_entropy) 

Parameters Used: The uiqid() function in PHP accepts two parameters. 

1. $prefix : It is an optional parameter which specifies a prefix to the unique id. It must be string.
2. $more_entropy : It is an optional parameter which specifies more entropy at the end of the return value which makes the id more unique.The default value is FALSE, which returns 13 characters long string whereas when it is set to TRUE, the return string is 23 characters long.

Return Value: It returns timestamp based unique identifier as a string.
Errors And Exceptions: 

1. The uniqid() function tries to create unique identifier, but it does not guarantee 100% uniqueness of return value.
2. Since most systems adjust system clock by NTP or like, system time is changed constantly. Therefore, it is possible that this function does not return unique ID for the process/thread.

Below programs illustrate the uniqid() function:
Program 1: 

php

Output:  

3b2c662647f18

Program 2: 

php

$myuid = uniqid('gfg');

echo $myuid;

?>

Output:  

gfg5b2b451823970

Program 3: 

php

$myuid = uniqid('gfg', true);

echo $myuid;

?>

gfg5b2b4555ab6bd7.27884925