What are common pitfalls when generating unique random numbers in PHP?

Common pitfalls when generating unique random numbers in PHP include using functions like rand() which may not produce truly unique numbers, and not properly seeding the random number generator, leading to predictable results. To generate unique random numbers, it is recommended to use functions like mt_rand() which provide a higher degree of randomness and to seed the random number generator with a unique value.

// Generate unique random number using mt_rand() with a seeded random number generator
$seed = uniqid();
mt_srand(crc32($seed));
$unique_random_number = mt_rand();
echo $unique_random_number;