# 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 common functions, the compatibility functions are always available, as long as their dependencies are met.

- Password Hashing
  - Dependencies
  - Constants
  - Function reference
- Hash (Message Digest)
  - Dependencies
  - Function reference
- Multibyte String
  - Dependencies
  - Function reference
- Standard Functions
  - Dependencies
  - Function reference

## Password Hashing

This set of compatibility functions offers a “backport” of PHP’s standard Password Hashing extension that is otherwise available only since PHP 5.5.

### Dependencies

- PHP 5.3.7
- `CRYPT_BLOWFISH` support for `crypt()`

### Constants

- `PASSWORD_BCRYPT`
- `PASSWORD_DEFAULT`

### Function reference

`password_get_info`($hash)

  Parameters: | $hash (string) – Password hash
  Returns: | Information about the hashed password
  Return type: | array

  For more information, please refer to the PHP manual for password_get_info().

`password_hash`($password, $algo[, $options = array()])

  Parameters: | $password (string) – Plain-text password $algo (int) – Hashing algorithm $options (array) – Hashing options
  Returns: | Hashed password or FALSE on failure
  Return type: | string

  For more information, please refer to the PHP manual for 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

`password_needs_rehash`()

  Parameters: | $hash (string) – Password hash $algo (int) – Hashing algorithm $options (array) – Hashing options
  Returns: | TRUE if the hash should be rehashed to match the given algorithm and options, FALSE otherwise
  Return type: | bool

  For more information, please refer to the PHP manual for password_needs_rehash().

`password_verify`($password, $hash)

  Parameters: | $password (string) – Plain-text password $hash (string) – Password hash
  Returns: | TRUE if the password matches the hash, FALSE if not
  Return type: | bool

  For more information, please refer to the PHP manual for 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

`hash_equals`($known_string, $user_string)

  Parameters: | $known_string (string) – Known string $user_string (string) – User-supplied string
  Returns: | TRUE if the strings match, FALSE otherwise
  Return type: | string

  For more information, please refer to the PHP manual for hash_equals().

`hash_pbkdf2`($algo, $password, $salt, $iterations[, $length = 0[, $raw_output = FALSE]])

  Parameters: | $algo (string) – Hashing algorithm $password (string) – Password $salt (string) – Hash salt $iterations (int) – Number of iterations to perform during derivation $length (int) – Output string length $raw_output (bool) – Whether to return raw binary data
  Returns: | Password-derived key or FALSE on failure
  Return type: | string

  For more information, please refer to the PHP manual for hash_pbkdf2().

## Multibyte String

This set of compatibility functions offers limited support for PHP’s Multibyte String extension. 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 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

`mb_strlen`($str[, $encoding = NULL])

  Parameters: | $str (string) – Input string $encoding (string) – Character set
  Returns: | Number of characters in the input string or FALSE on failure
  Return type: | string

  For more information, please refer to the PHP manual for mb_strlen().

`mb_strpos`($haystack, $needle[, $offset = 0[, $encoding = NULL]])

  Parameters: | $haystack (string) – String to search in $needle (string) – Part of string to search for $offset (int) – Search offset $encoding (string) – Character set
  Returns: | Numeric character position of where $needle was found or FALSE if not found
  Return type: | mixed

  For more information, please refer to the PHP manual for mb_strpos().

`mb_substr`($str, $start[, $length = NULL[, $encoding = NULL]])

  Parameters: | $str (string) – Input string $start (int) – Position of first character $length (int) – Maximum number of characters $encoding (string) – Character set
  Returns: | Portion of $str specified by $start and $length or FALSE on failure
  Return type: | string

  For more information, please refer to the PHP manual for 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

`array_column`(array $array, $column_key[, $index_key = NULL])

  Parameters: | $array (array) – Array to fetch results from $column_key (mixed) – Key of the column to return values from $index_key (mixed) – Key to use for the returned values
  Returns: | An array of values representing a single column from the input array
  Return type: | array

  For more information, please refer to the PHP manual for array_column().

`hex2bin`($data)

  Parameters: | $data (array) – Hexadecimal representation of data
  Returns: | Binary representation of the given data
  Return type: | string

  For more information, please refer to the PHP manual for hex2bin().