bcit-ci/CodeIgniter

#######################
Compatibility Functions
#######################

CodeIgniter provides a set of compatibility functions that enable
you to use functions what are otherwise natively available in PHP,
but only in higher versions or depending on a certain extension.

Being custom implementations, these functions will also have some
set of dependencies on their own, but are still useful if your
PHP setup doesn't offer them natively.

.. note:: Much like the :doc:`common functions <common_functions>`, the
    compatibility functions are always available, as long as
    their dependencies are met.

.. contents::
  :local:

.. raw:: html

  <div class="custom-index container"></div>

****************
Password Hashing
****************

This set of compatibility functions offers a "backport" of PHP's
standard `Password Hashing extension <https://secure.php.net/password>`_
that is otherwise available only since PHP 5.5.

Dependencies
============

- ``CRYPT_BLOWFISH`` support for ``crypt()``

Constants
=========

- ``PASSWORD_BCRYPT``
- ``PASSWORD_DEFAULT``

Function reference
==================

.. php:function:: password_get_info($hash)

    :param    string    $hash: Password hash
    :returns:    Information about the hashed password
    :rtype:    array

    For more information, please refer to the `PHP manual for
    password_get_info() <https://secure.php.net/password_get_info>`_.

.. php:function:: password_hash($password, $algo[, $options = array()])

    :param    string    $password: Plain-text password
    :param    int    $algo: Hashing algorithm
    :param    array    $options: Hashing options
    :returns:    Hashed password or FALSE on failure
    :rtype:    string

    For more information, please refer to the `PHP manual for
    password_hash() <https://secure.php.net/password_hash>`_.

    .. note:: Unless you provide your own (and valid) salt, this function
        has a further dependency on an available CSPRNG source. Each
        of the following would satisfy that:
        - ``mcrypt_create_iv()`` with ``MCRYPT_DEV_URANDOM``
        - ``openssl_random_pseudo_bytes()``
        - /dev/arandom
        - /dev/urandom

.. php:function:: password_needs_rehash()

    :param    string    $hash: Password hash
    :param    int    $algo: Hashing algorithm
    :param    array    $options: Hashing options
    :returns:    TRUE if the hash should be rehashed to match the given algorithm and options, FALSE otherwise
    :rtype:    bool

    For more information, please refer to the `PHP manual for
    password_needs_rehash() <https://secure.php.net/password_needs_rehash>`_.

.. php:function:: password_verify($password, $hash)

    :param    string    $password: Plain-text password
    :param    string    $hash: Password hash
    :returns:    TRUE if the password matches the hash, FALSE if not
    :rtype:    bool

    For more information, please refer to the `PHP manual for
    password_verify() <https://secure.php.net/password_verify>`_.

*********************
Hash (Message Digest)
*********************

This compatibility layer contains backports for the ``hash_equals()``
and ``hash_pbkdf2()`` functions, which otherwise require PHP 5.6 and/or
PHP 5.5 respectively.

Dependencies
============

- None

Function reference
==================

.. php:function:: hash_equals($known_string, $user_string)

    :param    string    $known_string: Known string
    :param    string    $user_string: User-supplied string
    :returns:    TRUE if the strings match, FALSE otherwise
    :rtype:    string

    For more information, please refer to the `PHP manual for
    hash_equals() <https://secure.php.net/hash_equals>`_.

.. php:function:: hash_pbkdf2($algo, $password, $salt, $iterations[, $length = 0[, $raw_output = FALSE]])

    :param    string    $algo: Hashing algorithm
    :param    string    $password: Password
    :param    string    $salt: Hash salt
    :param    int    $iterations: Number of iterations to perform during derivation
    :param    int    $length: Output string length
    :param    bool    $raw_output: Whether to return raw binary data
    :returns:    Password-derived key or FALSE on failure
    :rtype:    string

    For more information, please refer to the `PHP manual for
    hash_pbkdf2() <https://secure.php.net/hash_pbkdf2>`_.

****************
Multibyte String
****************

This set of compatibility functions offers limited support for PHP's
`Multibyte String extension <https://secure.php.net/mbstring>`_. Because of
the limited alternative solutions, only a few functions are available.

.. note:: When a character set parameter is ommited,
    ``$config['charset']`` will be used.

Dependencies
============

- `iconv <https://secure.php.net/iconv>`_ extension

.. important:: This dependency is optional and these functions will
    always be declared. If iconv is not available, they WILL
    fall-back to their non-mbstring versions.

.. important:: Where a character set is supplied, it must be
    supported by iconv and in a format that it recognizes.

.. note:: For you own dependency check on the actual mbstring
    extension, use the ``MB_ENABLED`` constant.

Function reference
==================

.. php:function:: mb_strlen($str[, $encoding = NULL])

    :param    string    $str: Input string
    :param    string    $encoding: Character set
    :returns:    Number of characters in the input string or FALSE on failure
    :rtype:    string

    For more information, please refer to the `PHP manual for
    mb_strlen() <https://secure.php.net/mb_strlen>`_.

.. php:function:: mb_strpos($haystack, $needle[, $offset = 0[, $encoding = NULL]])

    :param    string    $haystack: String to search in
    :param    string    $needle: Part of string to search for
    :param    int    $offset: Search offset
    :param    string    $encoding: Character set
    :returns:    Numeric character position of where $needle was found or FALSE if not found
    :rtype:    mixed

    For more information, please refer to the `PHP manual for
    mb_strpos() <https://secure.php.net/mb_strpos>`_.

.. php:function:: mb_substr($str, $start[, $length = NULL[, $encoding = NULL]])

    :param    string    $str: Input string
    :param    int    $start: Position of first character
    :param    int    $length: Maximum number of characters
    :param    string    $encoding: Character set
    :returns:    Portion of $str specified by $start and $length or FALSE on failure
    :rtype:    string

    For more information, please refer to the `PHP manual for
    mb_substr() <https://secure.php.net/mb_substr>`_.

******************
Standard Functions
******************

This set of compatibility functions offers support for a few
standard functions in PHP that otherwise require a newer PHP version.

Dependencies
============

- None

Function reference
==================

.. php:function:: array_column(array $array, $column_key[, $index_key = NULL])

    :param    array    $array: Array to fetch results from
    :param    mixed    $column_key: Key of the column to return values from
    :param    mixed    $index_key: Key to use for the returned values
    :returns:    An array of values representing a single column from the input array
    :rtype:    array

    For more information, please refer to the `PHP manual for
    array_column() <https://secure.php.net/array_column>`_.