Multi document YAML reader for PHP

yaml-reader.php

<?php
/*
 * There is currently no pure PHP yaml parser capable of reading
 *  multi documents (--- separated). I have tested both spyc and Symfony's YAML.
 *
 * Therefore I parse YAML with Python, encode it to json and read the json in
 * PHP. The json is cached on disk.
 *
 * Public Domain by http://github.com/svenk
 */

function read_yamlfile($filename) {
	$cache_dir = dirname(__FILE__).'/cache';
	//global $cache_dir;

	// check if json file exists
	$cache_filename = $cache_dir . '/' . md5($filename) . ".yaml2json";
	
	#print "YAML: $cache_filename <br>".filemtime($cache_filename)."<br>";
	#print "FILE: $filename <br>".filemtime($filename)."<br>";
	#exit;
	
	/* Check for existence and validity of the cache file by comparing modification times */
	if(file_exists($cache_filename) and filemtime($cache_filename) >= filemtime($filename)) {
		return json_decode(file_get_contents($cache_filename), /* assoc: */ TRUE);
	}

	// create json file by creating a Python program that creates it.
	$python_prog = <<<PYTHON
#!/usr/bin/python
import yaml # pip install PyYAML / python-yaml
import json # included
from io import open # python 2/3 unicode
import sys

def slurp(filename):
	# read file in string 
	with open(filename, 'r', encoding='utf-8') as file:
		return file.read()

def yamlfile(filename):
	# load yaml markup into python structures
	try:
		talks = list(yaml.load_all(slurp(filename)))
	except yaml.composer.ComposerError as e:
		print "Compilation error in %s: %s" % (filename,str(e))
		sys.exit(1)
		
	return talks

json.dump(yamlfile(sys.argv[1]), sys.stdout)
sys.exit(0)
PYTHON;
	$python_command = $cache_dir . "/yaml2json.py";
	file_put_contents($python_command, $python_prog);
	$exec = "python $python_command $filename 2>&1";
	exec($exec, $output, $retval);
	$output = implode("\n",$output);
	if($retval != 0) {
		print "Error evaluating Yaml2Json when executing Python (<em>$exec</em>, Retval: $retval): <pre>$output</pre>";
		return null;
	}
	file_put_contents($cache_filename, $output);
	return json_decode($output, /* assoc: */ TRUE);
}

This is a python-workaround for reading in YAML files in PHP. Due to the file cache, it is not even slow.

Known limitations: Serialization of python data structures may fail if the python yaml parser detected something special, for instance date objects (i.e. a string 2017-11-03 which is parsed as a date). But it is easy to implement a fix for that.