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openssl_random_pseudo_bytes

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(PHP 5 >= 5.3.0, PHP 7)

openssl_random_pseudo_bytes — Generate a pseudo-random string of bytes

Description

openssl_random_pseudo_bytes ( int $length [, bool &$crypto_strong ] ) : string

Generates a string of pseudo-random bytes, with the number of bytes determined by the length parameter.

It also indicates if a cryptographically strong algorithm was used to produce the pseudo-random bytes, and does this via the optional crypto_strong parameter. It's rare for this to be FALSE, but some systems may be broken or old.

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Parameters

length

The length of the desired string of bytes. Must be a positive integer. PHP will try to cast this parameter to a non-null integer to use it.

crypto_strong

If passed into the function, this will hold a boolean value that determines if the algorithm used was "cryptographically strong", e.g., safe for usage with GPG, passwords, etc. TRUE if it did, otherwise FALSE

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Return Values

Returns the generated string of bytes on success, or FALSE on failure.

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Examples

Example #1 openssl_random_pseudo_bytes() example

<?php
for ($i = -1; $i <= 4; $i++) {
    $bytes = openssl_random_pseudo_bytes($i, $cstrong);
    $hex   = bin2hex($bytes);

    echo "Lengths: Bytes: $i and Hex: " . strlen($hex) . PHP_EOL;
    var_dump($hex);
    var_dump($cstrong);
    echo PHP_EOL;
}
?>

The above example will output something similar to:

Lengths: Bytes: -1 and Hex: 0
string(0) ""
NULL

Lengths: Bytes: 0 and Hex: 0
string(0) ""
NULL

Lengths: Bytes: 1 and Hex: 2
string(2) "42"
bool(true)

Lengths: Bytes: 2 and Hex: 4
string(4) "dc6e"
bool(true)

Lengths: Bytes: 3 and Hex: 6
string(6) "288591"
bool(true)

Lengths: Bytes: 4 and Hex: 8
string(8) "ab86d144"
bool(true)

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See Also

  • random_bytes() - Generates cryptographically secure pseudo-random bytes
  • bin2hex() - Convert binary data into hexadecimal representation
  • crypt() - One-way string hashing
  • mt_rand() - Generate a random value via the Mersenne Twister Random Number Generator
  • uniqid() - Generate a unique ID
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Document created the 30/01/2003, last modified the 26/10/2018
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References

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