cURL request won't work with data from fetch API - php

Question

I'm sending some data with the fetch API to a translate.php file, here is my JS code:
const translation = {
word: 'Hello'
};
fetch('http://yandex.local/translate.php', {
method: 'POST',
body: JSON.stringify(translation),
headers: {
'Content-Type': 'application/json'
}
}).then(res => {
return res.text();
}).then(text => {
console.log(text);
})
Here is how I try to get the data on the translate.php:
$postData = json_decode(file_get_contents("php://input"), true);
$word = $postData['word'];
Here is my cURL request:
$word = $postData['word'];
$curl = curl_init();
$request = '{
"texts": "Hello",
"targetLanguageCode": "ru",
"sourceLanguageCode": "en"
}';
curl_setopt($curl, CURLOPT_URL, 'https://translate.api.cloud.yandex.net/translate/v2/translate');
curl_setopt($curl, CURLOPT_POST, true);
curl_setopt($curl, CURLOPT_HTTPHEADER, array(
"Authorization: Api-Key 123456",
"Content-Type: application/json"
));
curl_setopt($curl, CURLOPT_POSTFIELDS, $request);
curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);
$result = curl_exec($curl);
$err = curl_error($curl);
if($err) {
echo 'Curl Error: ' . $err;
} else {
$response = json_decode($result, true);
print_r($response['translations']['0']['text']);
}
curl_close($curl);
When I'm runing this code I get the translation of Hello in russian which is Привет. But if I replace "Hello" in the request object by $word I got the error: Trying to access array offset on value of type null
Here is the way I rewrite the request object:
$request = '{
"texts": $word,
"targetLanguageCode": "ru",
"sourceLanguageCode": "en"
}';
When I check the XHR of my translate.php all seems ok, I have a status 200 and the request payload shows my data. Also the word "hello" displays correctly in the console of my index.php

Answer 1

Don't ever create JSON strings by hand (i.e. I mean by hard-coding the JSON text directly into a string variable). It can lead to all kinds of syntax issues accidentally.
Please replace
$request = '{
"texts": "Hello",
"targetLanguageCode": "ru",
"sourceLanguageCode": "en"
}';
with
$requestObj = array(
"texts" => $word,
"targetLanguageCode" => "ru",
"sourceLanguageCode" => "en"
);
$request = json_encode($requestObj);
This will produce a more reliable output, and also include the $word variable correctly.
P.S. Your actual issue was that in PHP, variables are not interpolated inside a string unless that string is double-quoted (see the manual). Your $request string is single-quoted.
Therefore $word inside your $request string was not changed into "Hello" but left as the literal string "$word". And also since you removed the quotes around it, when the remote server tries to parse that it will not be valid JSON, because a text variable in JSON must have quotes around it. This is exactly the kind of slip-up which is easy to make, and why I say not to build your JSON by hand!
Your version would output
{"texts":$word,"targetLanguageCode":"ru","sourceLanguageCode":"en"}
whereas my version will (correctly) output:
{"texts":"Hello","targetLanguageCode":"ru","sourceLanguageCode":"en"}
(Of course I should add, given the comment thread above, that regardless of my changes, none of this will ever work unless you send a correct POST request to translate.php containing the relevant data to populate $word in the first place.)