str_inflect.php

<?php

function str_inflect(string $value, Countable|int|float $count = null, bool $format = false, bool $spellout = false): string
{
	preg_match('/^(?:(?<verb>is(?: an?)?|are)\s+)?(?:(?<count>\d+(?:[,.]\d+)?)\s+)?(?<value>.*)/m', $value, $matches);
	
	// Get rid of any commas in the input value
	$matches['count'] = str_replace(',', '', $matches['count']);
	
	// This is used for pluralization, but whatever input was provided
	// in $value will be used when building the final string
	$count = match (true) {
		is_countable($count) => count($count),
		null !== $count => $count,
		str_contains($matches['count'], '.') => (float) $matches['count'],
		'' !== $matches['count'] => (int) $matches['count'],
		default => throw new InvalidArgumentException('You must provide a count to str_inflect()'),
	};
	
	$formatted = match (true) {
		$spellout && $format => throw new InvalidArgumentException('You cannot use both `format` and `spellout` when calling str_inflect()'),
		$format => Number::format($count),
		$spellout => Number::spell($count),
		default => $matches['count'],
	};
	
	$singular = (int) ceil($count) === 1;
	
	// Allow for "is a" or "is an" cases
	$is = 'are' === $matches['verb'] ? 'is' : $matches['verb'];
	
	return str($matches['value'])
		->when($singular, fn($str) => $str->singular(), fn($str) => $str->plural())
		->when('' !== $matches['count'], fn($str) => $str->prepend("{$formatted} "))
		->when(! empty($matches['verb']), fn($str) => $str->prepend($singular ? "{$is} " : 'are '))
		->toString();
}