Что делать, если разделителей - несколько?

$first = explode(".?!", file_get_contents("inputfile001.txt") ?: '');

$first = explode("." or "?" or "!", file_get_contents("inputfile001.txt") ?: '');

$first = explode("." || "?" || "!", file_get_contents("inputfile001.txt") ?: '');

<?php
$text = "a;b,c.d|e";
$delimiters = [";", ",", ".", "|"];
$pattern = '/[' . implode('', array_map('preg_quote', $delimiters)) . ']/';
$result = preg_split($pattern, $text);
var_dump($result);

<?php
function splitByChars(string $text, array $delimiters, bool $dropEmpty = true): array {
    $escaped = array_map(
        static fn ($d) => preg_quote($d, '/'),
        $delimiters
    );
 
    $pattern = '/[' . implode('', $escaped) . ']/u';
    $flags = $dropEmpty ? PREG_SPLIT_NO_EMPTY : 0;
 
    return preg_split($pattern, $text, -1, $flags);
}
 
$text = "a;b,c.d|e";
$parts = splitByChars($text, [";", ",", ".", "|"]);
var_dump($parts);

$sentences = preg_split('/[.?!]/', $text);

$sentences = preg_split('/(?<=[.?!])\s+/i', $text);

$sentences = preg_split('/[.?!]\K\s+/i', $text);