Função para mesclar múltiplos espaços, quebras de linhas ou tabs em um único espaço.

merge_white_spaces.php

<?php

function merge_white_spaces($string) {
    // Remove multiple line breaks
    $string = preg_replace("/[\n\r]{3,}|[\r\n]{3,}|[\n]{3,}|[\r]{3,}/", PHP_EOL . PHP_EOL, $description);

    // Remove tabs
    $string = preg_replace("/\t+/", "", $description);

    // Remove multiple spaces (the character " " is used instead \s because the second removes line breaks too)
    $string = preg_replace("/[ ]{2,}/", " ", $description);

    $string = trim($description);

    return $string;
}