Add functions to parse and get some values from php.ini.

Get upload limits from php.ini. These functions will be used for checking
against upload limits and to give information in the frontend.
Wasn't sure in which file to put these functions, so I created a new
one include/environment.php.

include/environment.php

@@ -0,0 +1,66 @@
+<?php
+/**
+ * @file include/environment.php
+ * @brief Functions related to system/environment tasks.
+ *
+ * This file contains some functions to check the environment/system.
+ */
+
+/**
+ * @brief Get some upload related limits from php.ini.
+ *
+ * This function returns values from php.ini like \b post_max_size,
+ * \b max_file_uploads, \b upload_max_filesize.
+ *
+ * @return array associative array
+ *   * \e int \b post_max_size the maximum size of a complete POST in bytes
+ *   * \e int \b upload_max_filesize the maximum size of one file in bytes
+ *   * \e int \b max_file_uploads maximum number of files in one POST
+ *   * \e int \b max_upload_filesize min(post_max_size, upload_max_filesize)
+ */
+function getPhpiniUploadLimits() {
+	$ret = array();
+
+	// max size of the complete POST
+	$ret['post_max_size'] = phpiniSizeToBytes(ini_get('post_max_size'));
+	// max size of one file
+	$ret['upload_max_filesize'] = phpiniSizeToBytes(ini_get('upload_max_filesize'));
+	// catch a configuration error where post_max_size < upload_max_filesize
+	$ret['max_upload_filesize'] = min(
+			$ret['post_max_size'],
+			$ret['upload_max_filesize']
+			);
+	// maximum number of files in one POST
+	$ret['max_file_uploads'] = intval(ini_get('max_file_uploads'));
+
+	return $ret;
+}
+
+/**
+ * @brief Parses php_ini size settings to bytes.
+ *
+ * This function parses common size setting from php.ini files to bytes.
+ * e.g. post_max_size = 8M ==> 8388608
+ *
+ * \note This method does not recognise other human readable formats like
+ * 8MB, etc.
+ *
+ * @todo Make this function more universal useable. MB, T, etc.
+ *
+ * @param string $val value from php.ini e.g. 2M, 8M
+ * @return int size in bytes
+ */
+function phpiniSizeToBytes($val) {
+	$val = trim($val);
+	$unit = strtolower($val[strlen($val)-1]);
+	switch($unit) {
+		case 'g':
+			$val *= 1024;
+		case 'm':
+			$val *= 1024;
+		case 'k':
+			$val *= 1024;
+	}
+
+	return (int)$val;
+}