Nearby location-I want to develop a webpage similar to the mobile phone end of Meituan to implement a function to implement nearby merchants

Based on the map of Meituan or Baidu, you can obtain the user's location information and then find the information of the surrounding merchants from the database. After reading the Android client and webpage of Baidu glutinous rice, the distance between the merchants around the same location is actually different. I also encountered this problem, when we were doing this, we used the Html5 method to obtain the longitude and latitude. we used the method to calculate the latitude and longitude distance between two points. why is the calculation inaccurate, I just want to do the same thing with the group. Note that the PHP language has implemented the above-mentioned technology to help the nearby location of the php imitation Meituan to locate the html5

Based on the map of Meituan or Baidu, you can obtain the user's location information and then find the information of the surrounding merchants from the database. After reading the Android client and webpage of Baidu glutinous rice, the distance between the merchants around the same location is actually different. I also encountered this problem, when we were doing this, we used the Html5 method to obtain the longitude and latitude. we used the method to calculate the latitude and longitude distance between two points. why is the calculation inaccurate, I just want to do the same thing with the group. Note that the PHP language is used to help technical experts.