How can the issue of double line breaks instead of single line breaks be resolved when converting HTML email to plain text email in PHP?

The issue of double line breaks instead of single line breaks when converting HTML email to plain text email in PHP can be resolved by using the PHP `strip_tags()` function to remove HTML tags and then using the `preg_replace()` function to replace double line breaks with single line breaks.

$html_email = "<p>This is a sample HTML email.</p><p>It contains multiple paragraphs.</p>";
$plain_text_email = strip_tags($html_email); // Remove HTML tags
$plain_text_email = preg_replace("/(\r\n|\r|\n){2}/", "\n", $plain_text_email); // Replace double line breaks with single line breaks

echo $plain_text_email;