Ограничения размера текста Yahoo YQL

Я пытаюсь использовать Yahoo Content Analysis на трех простых текстах.

Как это работает, но если я увеличу длину строки в командах substr, я получу:

{"error":{"lang":"en-US","description":"Unknown error","status":"500"}}

Кто-нибудь может объяснить, почему это происходит? Согласно документации API должен принимать гораздо более крупные строки.

Также я не могу понять, почему лимит отличается на строку. Есть идеи?

Вот мой код

<?php

/**
* Function to use Yahoo to analyse some simple text
* @param String $text
* @param String $format
* @return String $content
*/
function yahoo_content_analysis($text, $format = 'json')
{
$url = "http://query.yahooapis.com/v1/public/yql";

$query = 'SELECT * FROM contentanalysis.analyze WHERE text = "' . $text . '"';

$characters = array(' ', '=', '"');
$replacements = array('%20', '%3D', '%22');

$query = str_replace($characters, $replacements, $query);

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, "q=$query&format=$format");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_AUTOREFERER, true);
$response = curl_exec($ch);
$headers = curl_getinfo($ch);
curl_close($ch);

return $response;
}

// Text taken from wikipedia
$text1 = 'Computer programming (often shortened to programming or coding) is the process of designing, writing, testing, debugging, and maintaining the source code of computer programs.';
$text2 = 'For the thousands of refugees and migrants landing on its beaches every day Greece Lesbos island is a step to safety and a brighter future in Europe';
$text3 = 'Hurricane Gert was a large tropical cyclone that caused extensive flooding throughout Central America and Mexico in September 1993. It originated over the southwestern Caribbean Sea and briefly attained tropical storm strength before crossing Nicaragua, Honduras, and the Yucatán Peninsula.';

// {"error":{"lang":"en-US","description":"Unknown error","status":"500"}}

$text1 = substr($text1, 0, 120);
echo $text1 . PHP_EOL;
$response1 = yahoo_content_analysis($text1);
echo $response1 . PHP_EOL; // json

echo PHP_EOL;

$text2 = substr($text2, 0, 116);
echo $text2 . PHP_EOL;
$response2 = yahoo_content_analysis($text2);
echo $response2 . PHP_EOL; // json

echo PHP_EOL;

$text3 = substr($text3, 0, 124);
echo $text3 . PHP_EOL;
$response3 = yahoo_content_analysis($text3);
echo $response3 . PHP_EOL; // json