(PHP 5 >= 5.1.2, PHP 7, PHP 8, PECL hash >= 1.1)
hash_init — Initialize an incremental hashing context
$algo,$flags = 0,$key = "",$options = []
algo
Name of selected hashing algorithm (e.g. "sha256").
For a list of supported algorithms see hash_algos().
Note:
Non-cryptographic hash functions are not allowed if the
HASH_HMACflag is specified.
flags
Optional settings for hash generation, currently supports only one option:
HASH_HMAC. When specified, the key
must be specified.
key
When HASH_HMAC is specified for flags,
a shared secret key to be used with the HMAC hashing method must be supplied in this
parameter.
options
An array of options for the various hashing algorithms.
Currently, only the "seed" parameter is
supported by the MurmurHash variants.
Returns a Hashing Context for use with hash_update(), hash_update_stream(), hash_update_file(), and hash_final().
Throws a ValueError exception if
algo is unknown or is a non-cryptographic hash
function, or if key is empty.
| Version | Description |
|---|---|
| 8.1.0 | The options parameter has been added. |
| 8.0.0 |
Now throws an ValueError exception if the
algo is unknown or is a non-cryptographic hash
function, or if key is empty. Previously,
false was returned and an E_WARNING message was
emitted.
|
| 7.2.0 | Usage of non-cryptographic hash functions (adler32, crc32, crc32b, fnv132, fnv1a32, fnv164, fnv1a64, joaat) with HASH_HMAC was disabled. |
| 7.2.0 | Return HashContext instead of resource. |
Example #1 Incremental hashing example
<?php
$hash = hash('sha256', 'The quick brown fox jumped over the lazy dog.');
$ctx = hash_init('sha256');
hash_update($ctx, 'The quick brown fox ');
hash_update($ctx, 'jumped over the lazy dog.');
$incremental_hash = hash_final($ctx);
echo $incremental_hash, PHP_EOL;
var_dump($hash === $incremental_hash);
?>The above example will output:
68b1282b91de2c054c36629cb8dd447f12f096d3e3c587978dc2248444633483 bool(true)