从PHP中的字符串中获取特定数据

Question

说明:修改下面的代码，以便打印以下内容

CS 116 01 amulahuw
CS 116 01 amukher1
CS 116 01 amukher1
CS 116 02 amukher1
CS 116 02 gpcorser
CS 116 02 gpcorser

我在打印用户名(amulahuw，amukher1..etc)时遇到问题

<?php



/*
* 提示：该行代码过长，系统自动注释不进行高亮。一键复制会移除系统注释 
* $jsonString = '{"courses":[{"academicLevel":"UG","capacity":"28","comments":[],"courseNumber":"116","credit":"4","description":"This course presents an introduction to the concepts and techniques of computer programming. Emphasis is placed on developing the students ability to apply problem-solving strategies to design algorithms and to implement these algorithms in the Java Programming language.","instructors":[{"username":"amulahuw","name":"A. Mulahuwaish"}],"lineNumber":"0624","location":"UC","meetingTimes":[{"method":"LEC","building":"SE","room":"135","days":"MW","startTime":"10:30 AM","endTime":"12:20 PM","dates":"08\/26\/2019-12\/07\/2019","instructor":"amulahuw"},{"method":"FNL","building":"SE","room":"135","days":"M","startTime":"10:30 AM","endTime":"12:20 PM","dates":"12\/08\/2019-12\/14\/2019"}],"prefix":"CS","prerequisites":"MATH 103 or equivalent (Previous, Required) CS 105 (Previous, Required)  ","seatsAvailable":"4","section":"01","status":"Open","term":"19\/FA","title":"Computer Programming I"},{"academicLevel":"UG","capacity":"30","comments":[],"courseNumber":"116","credit":"4","description":"This course presents an introduction to the concepts and techniques of computer programming. Emphasis is placed on developing the students ability to apply problem-solving strategies to design algorithms and to implement these algorithms in the Java Programming language.","instructors":[{"username":"amukher1","name":"A. Mukherjee"}],"lineNumber":"0610","location":"UC","meetingTimes":[{"method":"LEC","building":"SE","room":"145","days":"TR","startTime":"08:30 AM","endTime":"10:20 AM","dates":"01\/14\/2019-04\/27\/2019","instructor":"amukher1"},{"method":"FNL","building":"SE","room":"145","days":"T","startTime":"08:30 AM","endTime":"10:20 AM","dates":"04\/29\/2019-05\/04\/2019"}],"prefix":"CS","prerequisites":"MATH 103 or equivalent (Previous, Required) CS 105 (Previous, Required)  ","seatsAvailable":"7","section":"01","status":"Open","term":"19\/WI","title":"Computer Programming I"},{"academicLevel":"UG","capacity":"29","comments":[],"courseNumber":"116","credit":"4","description":"This course presents an introduction to the concepts and techniques of computer programming. Emphasis is placed on developing the students ability to apply problem-solving strategies to design algorithms and to implement these algorithms in the Java Programming language.","instructors":[{"username":"amukher1","name":"A. Mukherjee"}],"lineNumber":"0590","location":"UC","meetingTimes":[{"method":"LEC","building":"SE","room":"145","days":"TR","startTime":"08:30 AM","endTime":"10:20 AM","dates":"01\/13\/2020-05\/02\/2020","instructor":"amukher1"}],"prefix":"CS","prerequisites":"MATH 103 or equivalent (Previous, Required) CS 105 (Previous, Required)  ","seatsAvailable":"4","section":"01","status":"Open","term":"20\/WI","title":"Computer Programming I"},{"academicLevel":"UG","capacity":"28","comments":[],"courseNumber":"116","credit":"4","description":"This course presents an introduction to the concepts and techniques of computer programming. Emphasis is placed on developing the students ability to apply problem-solving strategies to design algorithms and to implement these algorithms in the Java Programming language.","instructors":[{"username":"amukher1","name":"A. Mukherjee"}],"lineNumber":"0626","location":"UC","meetingTimes":[{"method":"LEC","building":"SE","room":"145","days":"TR","startTime":"08:30 AM","endTime":"10:20 AM","dates":"08\/26\/2019-12\/07\/2019","instructor":"amukher1"},{"method":"FNL","building":"SE","room":"145","days":"T","startTime":"08:30 AM","endTime":"10:20 AM","dates":"12\/08\/2019-12\/14\/2019"}],"prefix":"CS","prerequisites":"MATH 103 or equivalent (Previous, Required) CS 105 (Previous, Required)  ","seatsAvailable":"10","section":"02","status":"Open","term":"19\/FA","title":"Computer Programming I"},{"academicLevel":"UG","capacity":"30","comments":[],"courseNumber":"116","credit":"4","description":"This course presents an introduction to the concepts and techniques of computer programming. Emphasis is placed on developing the students ability to apply problem-solving strategies to design algorithms and to implement these algorithms in the Java Programming language.","instructors":[{"username":"gpcorser","name":"G. Corser"}],"lineNumber":"0612","location":"UC","meetingTimes":[{"method":"LEC","building":"SE","room":"145","days":"MW","startTime":"12:30 PM","endTime":"02:20 PM","dates":"01\/14\/2019-04\/27\/2019","instructor":"gpcorser"},{"method":"FNL","building":"SE","room":"145","days":"M","startTime":"12:30 PM","endTime":"02:20 PM","dates":"04\/29\/2019-05\/04\/2019"}],"prefix":"CS","prerequisites":"MATH 103 or equivalent (Previous, Required) CS 105 (Previous, Required)  ","seatsAvailable":"5","section":"02","status":"Open","term":"19\/WI","title":"Computer Programming I"},{"academicLevel":"UG","capacity":"29","comments":[],"courseNumber":"116","credit":"4","description":"This course presents an introduction to the concepts and techniques of computer programming. Emphasis is placed on developing the students ability to apply problem-solving strategies to design algorithms and to implement these algorithms in the Java Programming language.","instructors":[{"username":"gpcorser","name":"G. Corser"}],"lineNumber":"0592","location":"UC","meetingTimes":[{"method":"LEC","building":"SE","room":"145","days":"MW","startTime":"12:30 PM","endTime":"02:20 PM","dates":"01\/13\/2020-05\/02\/2020","instructor":"gpcorser"}],"prefix":"CS","prerequisites":"MATH 103 or equivalent (Previous, Required) CS 105 (Previous, Required)  ","seatsAvailable":"0","section":"02","status":"Clsd","term":"20\/WI","title":"Computer Programming I"}]}';
*/

$obj = json_decode($jsonString);

foreach ($obj->courses as $course) {
  echo $course->prefix . " " . $course->courseNumber . " " . $course->section . " " . $course->username . "\n" ;
}

我期待它给我在数据中的用户名，但没有错误信息，它没有给我任何东西。

美化JSON：

{
  "courses": [
    {
      "academicLevel": "UG",
      "capacity": "28",
      "comments": [],
      "courseNumber": "116",
      "credit": "4",
      "description": "This course presents an introduction to the concepts and techniques of computer programming. Emphasis is placed on developing the students ability to apply problem-solving strategies to design algorithms and to implement these algorithms in the Java Programming language.",
      "instructors": [
        {
          "username": "amulahuw",
          "name": "A. Mulahuwaish"
        }
      ],
      "lineNumber": "0624",
      "location": "UC",
      "meetingTimes": [
        {
          "method": "LEC",
          "building": "SE",
          "room": "135",
          "days": "MW",
          "startTime": "10:30 AM",
          "endTime": "12:20 PM",
          "dates": "08/26/2019-12/07/2019",
          "instructor": "amulahuw"
        },
        {
          "method": "FNL",
          "building": "SE",
          "room": "135",
          "days": "M",
          "startTime": "10:30 AM",
          "endTime": "12:20 PM",
          "dates": "12/08/2019-12/14/2019"
        }
      ],
      "prefix": "CS",
      "prerequisites": "MATH 103 or equivalent (Previous, Required) CS 105 (Previous, Required)  ",
      "seatsAvailable": "4",
      "section": "01",
      "status": "Open",
      "term": "19/FA",
      "title": "Computer Programming I"
    },
    {
      "academicLevel": "UG",
      "capacity": "30",
      "comments": [],
      "courseNumber": "116",
      "credit": "4",
      "description": "This course presents an introduction to the concepts and techniques of computer programming. Emphasis is placed on developing the students ability to apply problem-solving strategies to design algorithms and to implement these algorithms in the Java Programming language.",
      "instructors": [
        {
          "username": "amukher1",
          "name": "A. Mukherjee"
        }
      ],
      "lineNumber": "0610",
      "location": "UC",
      "meetingTimes": [
        {
          "method": "LEC",
          "building": "SE",
          "room": "145",
          "days": "TR",
          "startTime": "08:30 AM",
          "endTime": "10:20 AM",
          "dates": "01/14/2019-04/27/2019",
          "instructor": "amukher1"
        },
        {
          "method": "FNL",
          "building": "SE",
          "room": "145",
          "days": "T",
          "startTime": "08:30 AM",
          "endTime": "10:20 AM",
          "dates": "04/29/2019-05/04/2019"
        }
      ],
      "prefix": "CS",
      "prerequisites": "MATH 103 or equivalent (Previous, Required) CS 105 (Previous, Required)  ",
      "seatsAvailable": "7",
      "section": "01",
      "status": "Open",
      "term": "19/WI",
      "title": "Computer Programming I"
    },
    {
      "academicLevel": "UG",
      "capacity": "29",
      "comments": [],
      "courseNumber": "116",
      "credit": "4",
      "description": "This course presents an introduction to the concepts and techniques of computer programming. Emphasis is placed on developing the students ability to apply problem-solving strategies to design algorithms and to implement these algorithms in the Java Programming language.",
      "instructors": [
        {
          "username": "amukher1",
          "name": "A. Mukherjee"
        }
      ],
      "lineNumber": "0590",
      "location": "UC",
      "meetingTimes": [
        {
          "method": "LEC",
          "building": "SE",
          "room": "145",
          "days": "TR",
          "startTime": "08:30 AM",
          "endTime": "10:20 AM",
          "dates": "01/13/2020-05/02/2020",
          "instructor": "amukher1"
        }
      ],
      "prefix": "CS",
      "prerequisites": "MATH 103 or equivalent (Previous, Required) CS 105 (Previous, Required)  ",
      "seatsAvailable": "4",
      "section": "01",
      "status": "Open",
      "term": "20/WI",
      "title": "Computer Programming I"
    },
    {
      "academicLevel": "UG",
      "capacity": "28",
      "comments": [],
      "courseNumber": "116",
      "credit": "4",
      "description": "This course presents an introduction to the concepts and techniques of computer programming. Emphasis is placed on developing the students ability to apply problem-solving strategies to design algorithms and to implement these algorithms in the Java Programming language.",
      "instructors": [
        {
          "username": "amukher1",
          "name": "A. Mukherjee"
        }
      ],
      "lineNumber": "0626",
      "location": "UC",
      "meetingTimes": [
        {
          "method": "LEC",
          "building": "SE",
          "room": "145",
          "days": "TR",
          "startTime": "08:30 AM",
          "endTime": "10:20 AM",
          "dates": "08/26/2019-12/07/2019",
          "instructor": "amukher1"
        },
        {
          "method": "FNL",
          "building": "SE",
          "room": "145",
          "days": "T",
          "startTime": "08:30 AM",
          "endTime": "10:20 AM",
          "dates": "12/08/2019-12/14/2019"
        }
      ],
      "prefix": "CS",
      "prerequisites": "MATH 103 or equivalent (Previous, Required) CS 105 (Previous, Required)  ",
      "seatsAvailable": "10",
      "section": "02",
      "status": "Open",
      "term": "19/FA",
      "title": "Computer Programming I"
    },
    {
      "academicLevel": "UG",
      "capacity": "30",
      "comments": [],
      "courseNumber": "116",
      "credit": "4",
      "description": "This course presents an introduction to the concepts and techniques of computer programming. Emphasis is placed on developing the students ability to apply problem-solving strategies to design algorithms and to implement these algorithms in the Java Programming language.",
      "instructors": [
        {
          "username": "gpcorser",
          "name": "G. Corser"
        }
      ],
      "lineNumber": "0612",
      "location": "UC",
      "meetingTimes": [
        {
          "method": "LEC",
          "building": "SE",
          "room": "145",
          "days": "MW",
          "startTime": "12:30 PM",
          "endTime": "02:20 PM",
          "dates": "01/14/2019-04/27/2019",
          "instructor": "gpcorser"
        },
        {
          "method": "FNL",
          "building": "SE",
          "room": "145",
          "days": "M",
          "startTime": "12:30 PM",
          "endTime": "02:20 PM",
          "dates": "04/29/2019-05/04/2019"
        }
      ],
      "prefix": "CS",
      "prerequisites": "MATH 103 or equivalent (Previous, Required) CS 105 (Previous, Required)  ",
      "seatsAvailable": "5",
      "section": "02",
      "status": "Open",
      "term": "19/WI",
      "title": "Computer Programming I"
    },
    {
      "academicLevel": "UG",
      "capacity": "29",
      "comments": [],
      "courseNumber": "116",
      "credit": "4",
      "description": "This course presents an introduction to the concepts and techniques of computer programming. Emphasis is placed on developing the students ability to apply problem-solving strategies to design algorithms and to implement these algorithms in the Java Programming language.",
      "instructors": [
        {
          "username": "gpcorser",
          "name": "G. Corser"
        }
      ],
      "lineNumber": "0592",
      "location": "UC",
      "meetingTimes": [
        {
          "method": "LEC",
          "building": "SE",
          "room": "145",
          "days": "MW",
          "startTime": "12:30 PM",
          "endTime": "02:20 PM",
          "dates": "01/13/2020-05/02/2020",
          "instructor": "gpcorser"
        }
      ],
      "prefix": "CS",
      "prerequisites": "MATH 103 or equivalent (Previous, Required) CS 105 (Previous, Required)  ",
      "seatsAvailable": "0",
      "section": "02",
      "status": "Clsd",
      "term": "20/WI",
      "title": "Computer Programming I"
    }
  ]
}

Answer 1

我是在PHP小提琴上运行它的，这给出了错误：

E_NOTICE : type 8 -- Undefined property: stdClass::$username -- at line 7
CS 116 01 
E_NOTICE : type 8 -- Undefined property: stdClass::$username -- at line 7
CS 116 01 
E_NOTICE : type 8 -- Undefined property: stdClass::$username -- at line 7
CS 116 01 
E_NOTICE : type 8 -- Undefined property: stdClass::$username -- at line 7
CS 116 02 
E_NOTICE : type 8 -- Undefined property: stdClass::$username -- at line 7
CS 116 02 
E_NOTICE : type 8 -- Undefined property: stdClass::$username -- at line 7
CS 116 02

我不太清楚为什么您没有收到这些错误，我也不太熟悉PHP --也许可以检查您的php.ini文件是否关闭了错误报告设置？

username不是课程的属性，而是课程讲师的属性。似乎每个课程只有一个讲师，所以您可以用$course->username替换$course->instructors[0]->username。

当然，如果您希望使用多个用户名，您应该循环使用它们或以某种方式加入它们，例如使用join(',', array_map(function(instructor) { return instructor->username }, $course->instructors))。也就是说，对于这样一门有多位教授的课程：

{
  "academicLevel": "UG",
  "capacity": "28",
  "comments": [],
  "courseNumber": "116",
  // ..
  "instructors": [
    {
      "username": "amulahuw",
      "name": "A. Mulahuwaish"
    },
    {
      "username": "jsmith",
      "name": "J. Smith"
    },
    {
      "username": "bhappy",
      "name": "B. Happy"
    },
  ],
  // ..
}

使用此代码片段：

foreach ($obj->courses as $course) {
  echo $course->prefix . " "
     . $course->courseNumber . " "
     . $course->section . " "
     . join(',', array_map(function($instructor) {
                   return $instructor->username;
                 },
                 $course->instructors))
     . "\n" ;
}

应该给你：

CS 116 01 amukher1,jsmith,bhappy

您是在询问如何在注释中增加instructors[0]。如果有多个教授，您需要增加它，或者以其他方式遍历教授(使用array_map()和join())是一种方法。但是，如果您可以假设每门课程最多有一位教授(如您的JSON示例中的那样)，则不需要增加它。