https://stackoverflow.com/questions/37002494/php-7-with-phpmyadmin-gives-lots-of-deprecation-notices
From that link, this are the changes you need to do (if you have ubuntu 16.04):
sudo nano /usr/share/php/php-gettext/streams.php
Line 48 StringReader Error.
Go to Line 52 and change
function StringReader ($str=”) {
TO
function __construct($str=”) {
Line 84 FileReader Error
Go to Line 90 and change
function FileReader($filename) {
to
function __construct($filename) {
Line 145 CacheFileReader error
Go to Line 146 and change
function CachedFileReader($filename) {
to
function __construct($filename) {
Using sudo nano /usr/share/php/php-gettext/gettext.php.
Line 36 gettext_reader { error
I think you get the gist now, go to line 101 and change
function gettext_reader($Reader, $enable_cache = true) {
To
function __construct($Reader, $enable_cache = true) {
