random_bytes
Get cryptographically secure random bytes
Description
string random_bytes(int $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
-
Any combination of operating system and PHP version not previously mentioned: /dev/urandom
-
If none of the sources are available or they all fail to generate
randomness, then a Random\RandomException
will be thrown.
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.
Parameters
-
length
-
The length of the random string that should be returned in bytes; must be 1
or greater.
Return Values
A string containing the requested number of cryptographically
secure random bytes.
Errors/Exceptions
-
If an appropriate source of randomness cannot be found,
a Random\RandomException will be thrown.
-
If the value of
length
is less than 1
,
a ValueError will be thrown.
Examples
Example #1 random_bytes example
<?php
$bytes = random_bytes(5);
var_dump(bin2hex($bytes));
?>
The above example will output
something similar to:
See Also
- Random\Randomizer::getBytes
- random_int
- bin2hex
- base64_encode