For more than 15 lakh (1.5 million) records, here’s a detailed recommendation:

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Best Choice: CSV (for large flat data)

Reason:

• CSV can be processed line-by-line with very low memory usage.
• PHP can stream through the file using fgetcsv() without loading everything into memory.
• JSON loads the entire file at once, which will likely crash or be too slow with 15+ lakh records.

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Example: Efficient CSV Reading in PHP (Memory-Friendly)

$handle = fopen("bigdata.csv", "r");
if ($handle !== FALSE) {
    while (($row = fgetcsv($handle, 0, ",")) !== FALSE) {
        // Process each row (e.g., insert into DB, print, etc.)
        // Example:
        // print_r($row);
    }
    fclose($handle);
}

• Efficient even for gigabyte-size CSV files.
• You can even add a counter if needed:

$count = 0;
while (($row = fgetcsv($handle, 0, ",")) !== FALSE) {
    $count++;
    // Process row
}
echo "Total rows: $count";

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Avoid JSON for 15+ Lakh Rows

phpCopyEdit$json = file_get_contents("bigdata.json"); //High memory usage
$data = json_decode($json, true);          // Very slow / may crash

Problems:

• Loads entire file into RAM.
• May hit PHP memory limits (e.g., 128MB or 512MB).
• Not suitable for huge datasets unless using chunked streaming, which is complex.

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Summary

Format	Best For	Handles 15+ lakh data?	Speed	Memory Use
CSV	Flat/tabular data	Yes	Fast	Low
JSON	Nested/complex data	No (not recommended)	Slower	High

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Final Advice

• Use CSV if your data is flat (like rows from a database or Excel).
• If you’re dealing with hierarchical or nested data and must use JSON, consider splitting the file into smaller parts or using streaming parsers like JSONMachine.