What are the potential issues when mixing HTML output with CSV file generation in PHP?

Mixing HTML output with CSV file generation in PHP can cause issues such as having the CSV data mixed with HTML tags, leading to corrupted CSV files. To solve this, you should separate the CSV generation logic from the HTML output by using output buffering and headers to force the browser to download the CSV file instead of displaying it as HTML.

<?php
// Start output buffering
ob_start();

// CSV generation logic
$csv_data = "Name,Email\nJohn Doe,johndoe@example.com\nJane Smith,janesmith@example.com";

// Set headers to force download
header('Content-Type: text/csv');
header('Content-Disposition: attachment; filename="data.csv"');

// Output the CSV data
echo $csv_data;

// Flush output buffer
ob_end_flush();