Naively add autocomplete attribute to Contact Form 7 inputs

cf7-autocomplete.php

<?php

/**
 * @param $content
 *
 * @return string|string[]
 */
function imp_wpcf7_form_elements( $content ) {
	$valid_autocomplete = [
		'name',
		'email',
		'url',
		'country',
		'country-name',
	];

	$matches = [];
	preg_match('/name="([a-zA-Z]*)"/', $content, $matches);

	// If there are no matches, just return
	if (count($matches) < 1) {
		return $content;
	}

	// If the attribute is not in the whitelist, return
	if ( !in_array(strtolower($matches[1]), $valid_autocomplete) ) {
		return $content;
	}

	// Find the position of it in the string again
	$str_pos = strpos( $content, 'name="' . $matches[1] . '"' );
	if ( $str_pos === false ) {
		return $content;
	}

	return substr_replace( $content, ' autocomplete="' . strtolower($matches[1]) . '" ', $str_pos, 0 );
}
add_filter( 'wpcf7_form_elements', 'imp_wpcf7_form_elements' );