PHP写文件到指定位置

 1 <?php
 2     $fp = fopen("output.json", "r+");
 3     $flag = fseek($fp, -3, SEEK_END);
 4     if(!$flag){
 5         echo "Offset success\r\n";
 6     }
 7     else{
 8         echo "Offset failed\n";
 9     }
10     $flag = fwrite($fp, ",\n{HelloWorld}\n]");
11     if($flag){
12         echo "Have written";
13     }
14     else{
15         echo "Write Failed";    
16     }
17  ?>

data=[
{latitude: 42.363400, longitude: -71.098465, info: 'Speed = 21'},
]

在Json字符串中添加项