如何从字符串右侧删除货币缩写？

Question

I have a sample array like this:

[
  "BTCUSD",
  "DASHBTC",
  "DOGEUSD",
  "LTCBTC",
  "LTCUSD",
  "SCBTC",
  "STEEMBTC",
  "WAVESBTC",
  "SNGLSBTC",
  "1STBTC",
  "DASHUSD",
  "BQXETH",
  "PTOYETH",
  "XAURETH",
  "BTCUSDT"
]

How to get just one currency for every string? I can't use explode because there isn't a single/static delimiter. I can't use substr() or strpos() because the substrings vary.

So how to split it?

Update

This is my expected output

[
   "BTC",
   "DASH",
   "DOGE",
   "LTC",
   "LTC",
   "SC",
   "STEEM",
   "WAVES",
   "SNGLS",
   "1ST",
   "DASH",
   "BQX",
   "PTOY",
   "XAUR",
   "BTC"
]

Answer 1

You need to have an array to your expected currencies and then filter against it.

Here is a quick and dirty solution: https://3v4l.org/6mMbN or with recursive function call: https://3v4l.org/mhjBD

<?php

$currencies = [
    'USD',
    'BTC',
    'DASH',
    'LTC',
    'SC',
    'STEEM',
    'WAVES',
    'SNGLS',
    '1ST',
    'BQX',
    'ETH',
    'PTOY',
    'XAUR',
    ];

$input = [
  "BTCUSD",
  "DASHBTC",
  "DOGEUSD",
  "LTCBTC",
  "LTCUSD",
  "SCBTC",
  "STEEMBTC",
  "WAVESBTC",
  "SNGLSBTC",
  "1STBTC",
  "DASHUSD",
  "BQXETH",
  "PTOYETH",
  "XAURETH",
  "BTCUSDT",
];

$output=[];
foreach($input as $doubleCurrency){
    foreach($currencies as $currency){
        $pattern = '/^'.$currency. '/';
        preg_match($pattern, $doubleCurrency, $matches);
        if(array_key_exists(0, $matches)){
            $output[]=$matches[0];
        }
    }
}

var_dump($output);