PHP while loop modify last iteration

Question

I am trying to generate a JSON file from PHP. So far I have the following output:

"students":[
    {"name": "John"},
    {"name": "Alex"},
    {"name": "Siri"},
]

There is a comma after each student, when I clearly have to remove the final comma. Normally I would perform a while loop with an if statement. However, my database structure makes this situation different.

My PHP code looks like so:

    while ($getschools = $schools->fetch_assoc()){
        $findschools = $dbcon->query("SELECT * 
            FROM school_".$getstate['texas']."
            WHERE students = '".$studentGPA['best']."'");       
        while ($beststudents = $findschools->fetch_assoc()){
            $jsonfield.= '{"name":"'.$getstudent['firstname'].'"},';
        }
    }

The code might have a few missing parts, but hopefully the context is clear. I am using php variables from previous fetch requests to acquire data from multiple tables.

In my example there are multiple tables corresponding to the schools in Texas. I am getting the firstnames of every student from those multiple schools (or tables). I am attempting to apply this information to a JSON output.

The $jsonfield line shows the loop portion of my code. I am trying to figure out how to implement a code like this in my example:

$i = 0;
$countstudents = $getschools->num_rows;
if ($i < $countstudents){
$jsonfield.=',';
}

This way my commas are only applied to the parts of my data that are not the final iteration of my loop.

user94559 · Accepted Answer · 2017-07-06 04:44:31Z

5

Please don't try to make JSON by hand. Try something like this instead:

$students = [];

// This would happen in your loop.    
$students[] = array("name" => "John");
$students[] = array("name" => "Alex");
$students[] = array("name" => "Siri");

// Feel free to drop the JSON_PRETTY_PRINT.
echo json_encode(array("students" => $students), JSON_PRETTY_PRINT) . "\n";

// Output:
// {
//     "students": [
//         {
//             "name": "John"
//         },
//         {
//             "name": "Alex"
//         },
//         {
//             "name": "Siri"
//         }
//     ]
// }

answered Jul 6, 2017 at 4:44

user94559

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1 Comment

Eng Cy Over a year ago

Yup, there is a ready php function to generate json string, no need to manually manipulating json file

Thamilhan · Accepted Answer · 2017-07-06 04:46:13Z

2

You have two options:

Method 1: rtrim

Use rtrim($jsonfield, ',')

Method 2: implode

Add to $jsonfield as array - $jsonfield[]=.... and then use implode(',', $jsonfield).

Important:

More than these, why do you want to generate JSON using loop? You can use json_encode function.

answered Jul 6, 2017 at 4:46

Thamilhan

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Comments

Kunal Awasthi · Accepted Answer · 2017-07-06 04:50:19Z

1

 while ($getschools = $schools-            >fetch_assoc()){ 
 $findschools = $dbcon->query("SELECT *     FROM school_".$getstate['texas']." WHERE      students = '".$studentGPA['best']."'"); 
   while ($beststudents = $findschools->fetch_assoc()){
  $jsonfield.= '{"name":"'.$getstudent['firstname'].'"},';
 $i = 0; 
 $countstudents = $getschool->num_rows;                  
if($i+1 < $countstudents){  //if next index is    smaller than the count then add comma else don't and loop will be terminated
    $jsonfield.=','; 
      }
   }
 }

answered Jul 6, 2017 at 4:50

Kunal Awasthi

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