Plural

gistfile1.php

<?php

function get_word_form( $count, $word_forms = [ 'предмет', 'предмета', 'предметов' ] ) {

	$count = preg_replace( '/[^\d]/', '', $count );
	$n100  = $count % 100;
	$n10   = $count % 10;
	if ( ( $n100 > 10 ) && ( $n100 < 20 ) ) {
		return $word_forms[2];
	} elseif ( $n10 == 1 ) {
		return $word_forms[0];
	} elseif ( ( $n10 >= 2 ) && ( $n10 <= 4 ) ) {
		return $word_forms[1];
	} else {
		return $word_forms[2];
	}

}