如何使用 PHP 从 CSV 文件读取一系列行到 JSON 数组来处理大型 ZCC8D68C551C4ADEAFDDZD4 文件？

Question

The target is how to read a range of rows/lines from large CSV file into a JSON array in order to handle large files and read the data in pagination method, each page fetches a range of lines ( ex page number 1 fetch from line 1 to 10, page number 2 fetch from line 11 to line 20, and so and ).

the below PHP script read from the being CSV file to the desired line ($desired_line), My question is how we can determine the starting line to read from a specific line ($starting_line)

<?php
// php function to convert csv to json format
function csvToJson($fname, $starting_line, $desired_line) {
    // open csv file
    if (!($fp = fopen($fname, 'r'))) {
        die("Can't open file...");
    }
    
    //read csv headers
    $key = fgetcsv($fp,"1024","\t");
    
    $line_counter = 0; 
 
    
    // parse csv rows into array
    $json = array();
        while (($row = fgetcsv($fp,"1024","\t")) && ($line_counter < $desired_line)) {
        $json[] = array_combine($key, $row);
        $line_counter++; 
    }
    
    // release file handle
    fclose($fp);
    
    // encode array to json
    return json_encode($json);
}



// Define the path to CSV file
$csv = 'file.csv';
print_r(csvToJson($csv, 20, 30));

?>

Answer 1

You should use functions like:

fgets() to read the file line by line

fseek() to move to the position of the last fgets() of the chunk

ftell() to read the position for fseek()

Something like this (it's only a schema):

<?php

...

$line_counter = 0;
$last_pos = ...
$fseek($fp,$last_pos);
while($line = fgets($fp)){ // read a line of the file
   $line_counter++;
   (...) // parse line of csv here
   if($line_counter == 100){
      $lastpos = ftell($fp);
      (...) // save the $lastpos for next reading cycle
      break;
   }
}

...

?>

You can also skip the fseek() and ftell() part and just count the lines every time from the beginning, but that will generally have to go through the whole file from the beginning till the desired lines.