我花了一段时间才弄明白，因为在应用程序屏幕上，我得到的只是 JSON Parse Error: '<' . 多亏了 error_log ，我在php中发现了以下错误：

[29-Jun-2018 19:35:34 America/Chicago] PHP Deprecated:  Automatically populating $HTTP_RAW_POST_DATA is deprecated and will be removed in a future version. To avoid this warning set 'always_populate_raw_post_data' to '-1' in php.ini and use the php://input stream instead. in Unknown on line 0
[29-Jun-2018 19:35:34 America/Chicago] PHP Warning:  explode() expects parameter 2 to be string, array given in React/user-image-upload.php on line 17
[29-Jun-2018 19:35:34 America/Chicago] PHP Warning:  end() expects parameter 1 to be array, null given in React/user-image-upload.php on line 18
[29-Jun-2018 19:35:34 America/Chicago] PHP Warning:  preg_match() expects parameter 2 to be string, array given in React/user-image-upload.php on line 27
[29-Jun-2018 19:35:34 America/Chicago] PHP Warning:  unlink() expects parameter 1 to be a valid path, array given in React/user-image-upload.php on line 30

下面是我上传图片的php代码：

<?php
         // Getting the received JSON into $json variable.
 $json = file_get_contents('php://input');

 // decoding the received JSON and store into $obj variable.
 $obj = json_decode($json,true);

$fileName = $obj["userimgSource"]; // The file name
$fileTmpLoc = $obj["userimgSource"]; // File in the PHP tmp folder
$fileType = $obj["userimgSourceType"]; // The type of file it is
$fileSize = $obj["userimgSourceSize"]; // File size in bytes
$fileErrorMsg = $_FILES["uploaded_file"]["error"]; // 0 for false... and 1 for true
$kaboom = explode(".", $fileName); // Split file name into an array using the dot
$fileExt = end($kaboom); // Now target the last array element to get the file extension
// START PHP Image Upload Error Handling --------------------------------------------------
if (!$fileTmpLoc) { // if file not chosen
    echo json_encode("ERROR: Please browse for a file before clicking the upload button.");
    exit();
} else if($fileSize > 5242880) { // if file size is larger than 5 Megabytes
    echo json_encode("ERROR: Your file was larger than 5 Megabytes in size.");
    unlink($fileTmpLoc); // Remove the uploaded file from the PHP temp folder
    exit();
} else if (!preg_match("/.(gif|jpg|jpe|jpeg|png)$/i", $fileName) ) {
     // This condition is only if you wish to allow uploading of specific file types    
     echo json_encode("ERROR: Your image was not .gif, .jpg, .jpe, or .png.");
     unlink($fileTmpLoc); // Remove the uploaded file from the PHP temp folder
     exit();
} 
// END PHP Image Upload Error Handling ----------------------------------------------------
// Place it into your "uploads" folder mow using the move_uploaded_file() function
$moveResult = move_uploaded_file($fileTmpLoc, "../profiles/uploads/$fileName");
// Check to make sure the move result is true before continuing
if ($moveResult != true) {
    echo json_encode("ERROR: File not uploaded. Try again.");
    unlink($fileTmpLoc); // Remove the uploaded file from the PHP temp folder
    exit();
}
if  ($moveResult == true) {
    $db = mysqli_connect("localhost", "root", "password", "photos");
    $sql = "INSERT INTO user_images (images,date) VALUES ('$fileName',CURDATE())";
    mysqli_query($db, $sql);
    echo json_encode("Success: File uploaded.");

}
unlink($fileTmpLoc); // Remove the uploaded file from the PHP temp folder
?>

在我向你们展示我所有的react原生代码之前，我只想说，我不熟悉如何在rn中上传图像。我在网上读了很多问题，想知道怎么做，还看了一些youtube视频。我不知道我是否应该使用 base64 （如果有人能向我解释一下，那就太好了），据我所知，我只是拉取图像路径、图像大小和图像类型，然后将该图像路径插入我的文件夹和数据库：

SelectPhoto = () =>{
ImagePicker.openPicker({
cropping: true,
title: 'Select an image',
isCamera: true,
}).then((imgResponse) => {
  console.log(imgResponse);
  let imgSource = { uri: imgResponse[0].path.replace(/^.*[\\\/]/, '') };
  this.setState({
    userimgSource: imgSource,
    userimgSourceType: imgResponse[0].mime,
    userimgSourceSize: imgResponse[0].size,
  });
});

}

UploadPhoto = () =>{
  fetch('https://www.example.com/React/user-image-upload.php', {
  method: 'POST',
  headers: {
    'Accept': 'application/json',
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    userimgSource : this.state.userimgSource,
    userimgSourceType: this.state.userimgSourceType,
    userimgSourceSize: this.state.userimgSourceSize,

  })

  }).then((response) => response.json())
      .then((responseJson) => {

        // Showing response message coming from server after inserting records.
        Alert.alert(responseJson);

      }).catch((error) => {
        console.error(error);
      });
}

这就是困惑所在。当我 console.log 我的 userimgSource: imgSource, userimgSourceType: imgResponse[0].mime, userimgSourceSize: imgResponse[0].size, i、 事实上，一定要得到正确的数据。我得到图像路径： IMG_2018629.png ，哑剧演员： image/png ，大小： 2,097,152 . php为什么不能从react native中获取数据呢？