(PHP 7, PHP 8)
random_bytes — Get cryptographically secure random bytes
Generates a string containing uniformly selected random bytes with the requested length.
As the returned bytes are selected completely randomly, the resulting string is likely to contain unprintable characters or invalid UTF-8 sequences. It may be necessary to encode it before transmission or display.
The randomness generated by this function is suitable for all applications, including the generation of long-term secrets, such as encryption keys.
The sources of randomness in the order of priority are as follows:
Linux: » getrandom(), /dev/urandom
FreeBSD >= 12 (PHP >= 7.3): » getrandom(), /dev/urandom
Windows (PHP >= 7.2): » CNG-API
Windows: » CryptGenRandom
macOS (PHP >= 8.2; >= 8.1.9; >= 8.0.22 if CCRandomGenerateBytes is available at compile time): CCRandomGenerateBytes()
macOS (PHP >= 8.1; >= 8.0.2): arc4random_buf(), /dev/urandom
NetBSD >= 7 (PHP >= 7.1; >= 7.0.1): arc4random_buf(), /dev/urandom
OpenBSD >= 5.5 (PHP >= 7.1; >= 7.0.1): arc4random_buf(), /dev/urandom
DragonflyBSD (PHP >= 8.1): » getrandom(), /dev/urandom
Solaris (PHP >= 8.1): » getrandom(), /dev/urandom
Note: Although this function was added to PHP in PHP 7.0, a » userland implementation is available for PHP 5.2 to 5.6, inclusive.
length
The length of the random string that should be returned in bytes; must be 1 or greater.
A string containing the requested number of cryptographically secure random bytes.
length is less than 1,
a ValueError will be thrown.
| Version | Description |
|---|---|
| 8.2.0 | In case of a CSPRNG failure, this function will now throw a Random\RandomException. Previously a plain Exception was thrown. |
Example #1 random_bytes() example
<?php
$bytes = random_bytes(5);
var_dump(bin2hex($bytes));
?>The above example will output something similar to:
string(10) "385e33f741"