PHP 7.1

Changed functions

getopt() has an optional third parameter that exposes the index of the next element in the argument vector list to be processed. This is done via a by-ref parameter.
getenv() no longer requires its parameter. If the parameter is omitted, then the current environment variables will be returned as an associative array.
get_headers() now has an additional parameter to enable for the passing of custom stream contexts.
output_reset_rewrite_vars() no longer resets session URL rewrite variables.
parse_url() is now more restrictive and supports RFC3986.
unpack() now accepts an optional third parameter to specify the offset to begin unpacking from.

file_get_contents() now accepts a negative seek offset if the stream is seekable.
tempnam() now emits a notice when falling back to the system's temp directory.

json_encode() now accepts a new option, JSON_UNESCAPED_LINE_TERMINATORS, to disable the escaping of U+2028 and U+2029 characters when JSON_UNESCAPED_UNICODE is supplied.

PDO::lastInsertId() for PostgreSQL will now trigger an error when nextval has not been called for the current session (the postgres connection).

pg_last_notice() now accepts an optional parameter to specify an operation. This can be done with one of the following new constants: PGSQL_NOTICE_LAST, PGSQL_NOTICE_ALL, or PGSQL_NOTICE_CLEAR.
pg_fetch_all() now accepts an optional second parameter to specify the result type (similar to the third parameter of pg_fetch_array()).
pg_select() now accepts an optional fourth parameter to specify the result type (similar to the third parameter of pg_fetch_array()).

session_start() now returns false and no longer initializes $_SESSION when it failed to start the session.

debug_zval_dump() now prints "int" instead of "long", and "float" instead of "double"
dirname() now optionally takes a second parameter, depth, to get the name of the directory depth levels up from the current directory.
getrusage() is now supported on Windows.
mktime() and gmmktime() functions no longer accept is_dst parameter.
preg_replace() function no longer supports "\e" (PREG_REPLACE_EVAL). preg_replace_callback() should be used instead.
setlocale() function no longer accepts category passed as string. LC_* constants must be used instead.
exec(), system() and passthru() functions have NULL byte protection now.
shmop_open() now returns a resource instead of an int, which has to be passed to shmop_size(), shmop_write(), shmop_read(), shmop_close() and shmop_delete().
substr() and iconv_substr() now return an empty string, if string is equal to start characters long.
xml_parser_free() is no longer sufficient to free the parser resource, if it references an object and this object references that parser resource. In this case it is necessary to additionally unset the $parser.

crypt() will now raise an E_NOTICE error if the salt parameter is omitted.
substr_compare() will now accept 0 for its length parameter.
unserialize() will now fail if passed serialised data that has been manipulated to attempt to instantiate an object without calling its constructor.

Uploads using the @file syntax are now only supported if the CURLOPT_SAFE_UPLOAD option is set to false. CURLFile should be used instead.

The source parameter of mcrypt_create_iv() now defaults to MCRYPT_DEV_URANDOM instead of MCRYPT_DEV_RANDOM.

stream_socket_enable_crypto() now allows the crypto_type parameter to be optional if the stream's SSL context includes the new crypto_type option.

pg_insert(), pg_select(), pg_update() and pg_delete() are no longer experimental.
pg_send_execute(), pg_send_prepare(), pg_send_query() and pg_send_query_params() will no longer block until query write completion if the underlying socket stream for the database connection is set to non-blocking mode.

ReflectionClass::newInstanceWithoutConstructor() now allows non-final internal classes to be instantiated.

set_error_handler() can now be called with NULL as an argument to reset the error handler.
When called with NULL, set_error_handler() and set_exception_handler() now return the previous error or exception handler, respectively.
json_encode() now accepts depth parameter.
The behaviour of pack() and unpack() with the "a" and "A" format codes has changed. Detailed notes on these changes are available.

MessageFormatter::format() and related functions now accept named arguments and mixed numeric and named arguments when PHP is linked to ICU 4.8 or later.
MessageFormatter::format() and related functions no longer error when an insufficient number of arguments have been provided. Instead, the placeholders will not be substituted.
MessageFormatter::format() and MessageFormatter::parse() are no longer limited to second precision when dealing with times.
IntlDateFormatter::__construct() and datefmt_create() now accept IntlTimeZone and DateTimeZone objects for the timezone argument, and IntlCalendar objects for the calendar argument. Furthermore, if the time zone is omitted and the calendar doesn't specify a time zone, PHP's default time zone from date_default_timezone_get() is now used instead of the default ICU time zone.
IntlDateFormatter::getCalendar() and datefmt_get_calendar() return false if the IntlDateFormatter object was created with an IntlCalendar instance instead of one of the IntlDateFormatter constants.
IntlDateFormatter::setCalendar() and datefmt_set_calendar() now accept IntlCalendar objects in addition to the IntlDateFormatter constants.
IntlDateFormatter::format() and datefmt_format() now accept IntlCalendar objects.