Helper functions to create or parse Mermaid API requests to implement your own mermaid rendering API/service

mermaidjs-pako-implementation-for-php.php

<?php
/**
 * Convert the given payload to a pako-compressed string, parsable by mermaid
 * @var object|array $item
 * @return string
 */
function payload_to_mermaid(object|array $item): string {
	return pako_compress(json_encode($item));
}

/**
 * Compress the given string with pako
 * @param string $s
 * @return string
 */
function pako_compress(string $s): string {
	$converted = mb_convert_encoding($s, "UTF-8");
	// level=9 is required for mermaid
	$inflated = zlib_encode($converted,  ZLIB_ENCODING_DEFLATE, 9);
	$encoded = base64_encode($inflated);
	// var_dump(dump_bin2hex($encoded));
	// replace those base64 characters
	$encoded = str_replace('/', '_', $encoded);
	$encoded = str_replace('+', '-', $encoded);
	
	return $encoded;
}

/**
 * Decompress as mermaid-specific pako payload.
 * If you want to implement your own mermaid rendering server/API, this is for you.
 * @param string $s
 * @return object|array
 */
function payload_from_mermaid(string $s): object|array {
	return json_decode(pako_decompress($s));
}

/**
 * Decompress the pako payload
 * @param string $s
 * @return mixed|string
 */
function pako_decompress(string $s): mixed {
	$decoded = str_replace('_', '/', $s);
	$decoded = str_replace('-', '/', $decoded);
	
	// append == for making it base64 decodable
	if (!str_ends_with($decoded, '==')) {
		$decoded .= "==";
	}
	
	$binary = base64_decode($decoded);
	$deflated = zlib_decode($binary);
	
	return $deflated;
}

/**
 * Create a new mermaid rendering request
 * @param string Your diagram-as-a-code
 * @param null|array additional mermaid rendering configuration
 * @return string
 */
function mermaid_request(string $mermaidDiagram, ?array $configuration = []): string {
	$configuration = $configuration ?? ['theme' => 'default'];
	return payload_to_mermaid([
		'code' => $mermaidDiagram,
		'mermaid' => $configuration
	]);
}

/**
 * Build a full rendering link to your mermaid instance
 * @param string $mermaidDiagram
 * @param null|array $configuration additional mermaid rendering configuration
 * @param string $baseUrl Defaults to mermaid.live but feel free to use your own rendering server
 * @param string $mode Either 'view' or 'edit'
 * @return string
 */
function build_mermaid_render_link(string $mermaidDiagram, ?array $configuration = [], string $baseUrl = 'http://mermaid.live/', $mode = 'view'): string {
	return $baseUrl 
		. ( $mode == 'view' ? 'view' : 'edit' )
		. '#pako:'
		. mermaid_request($mermaidDiagram, $configuration);
}

/**
 * Dump the given parameter as a formatted hex array.
 * @param string|array stringOrArray
 * @return string
 */
function dump_bin2hex(string|array $stringOrArray): string {
	$r = [];
	$size = is_string($stringOrArray) ? strlen($stringOrArray) : sizeof($stringOrArray);

	for ($i = 0; $i < $size; $i++) {
		$r[] = str_pad(dechex(ord($stringOrArray[$i])), 2, "0", STR_PAD_LEFT);
	}

	return implode(" ", $r);
}


echo build_mermaid_render_link(<<<PHP
C4Context

	title My second landscape
PHP
);

var_dump(payload_from_mermaid("eNqrVkrOT0lVslJyNnHOzytJrSiJyQPCkpLMkpxUBd9KheLU5Py8FIWcxLyU4uTEglQlHaXc1KLcxMwUJavo2FoA4LIWxg=="));