Given a WP REST API content list route, fetches all IDs, URLs, and Titles into a CSV file.

fetch-from-wp-rest-api.php

<?php
/**
 * Usage example: `php -f fetch-from-wp-rest-api.php https://wordpress.org/support/wp-json/wp/v2/articles helphub-list`
 */

$first_page         = file_get_contents( $argv[1] . '?per_page=100' );
$first_page_headers = parse_headers( $http_response_header );
$content            = json_decode( $first_page, true );

for ( $i = 2; $i < $first_page_headers['X-WP-TotalPages']; $i++ ) {
	$page    = file_get_contents( $argv[1] . '?per_page=100&page=' . $i );
	$page    = json_decode( $page, true );
	$content = array_merge( $content, $page );
}

$csv_lines = [
	implode( ',', [ 'ID', 'URL', 'Title' ] ),
];
foreach ( $content as $post ) {
	$csv_lines[] = implode(
		',',
		[ $post['id'], $post['link'], $post['title']['rendered'] ]
	);
}

if ( ! empty( $argv[2] ) ) {
	$filename = $argv[2] . '.csv';
} else {
	$filename = date( 'Y-m-d-H-i-s' ) . '.csv';
}
file_put_contents( $filename, implode( "\n", $csv_lines ) );
echo "Done.\n";

function parse_headers( $headers ) {
	$head = array();
	foreach ( $headers as $k => $v ) {
		$t = explode( ':', $v, 2 );
		if ( isset( $t[1] ) ) {
			$head[ trim( $t[0] ) ] = trim( $t[1] );
		} else {
			$head[] = $v;
			if ( preg_match( '#HTTP/[0-9\.]+\s+([0-9]+)#', $v, $out ) ) {
				$head['reponse_code'] = intval( $out[1] );
			}
		}
	}
	return $head;
}