Update README.md

Author: fabacino

README.md

@@ -2,3 +2,118 @@
 
 [![Build Status](https://travis-ci.org/fabacino/php-debug-functions.svg?branch=master)](https://travis-ci.org/fabacino/php-debug-functions)
 [![codecov](https://codecov.io/gh/fabacino/php-debug-functions/branch/master/graph/badge.svg)](https://codecov.io/gh/fabacino/php-debug-functions)
+
+A collection of simple debug functions which might be helpful in case a full-fledged debugger is not available.
+
+## Requirements
+
+The following versions of PHP are supported:
+
+* PHP 7.0
+* PHP 7.1
+* PHP 7.2
+
+## Installation
+
+TODO
+
+## Usage
+
+* `dbg`: Print out debug value.
+* `dbgr`: Return debug value.
+* `dbglog`: Log debug value into file.
+* `dbginit`: Initialize debug settings.
+
+The functions accept any value for debugging, as long as it can be passed as a variable.
+
+## Examples
+
+### Print values to standard output
+
+```php
+dbg(123);
+dbg('a string');
+dbg([
+    'token' => 'dp83kspo',
+    'is_default' => true
+]);
+```
+
+```
+// Output
+123
+a string
+Array
+(
+    [id] => 123
+    [token] => dp83kspo
+    [is_default] => true
+)
+```
+
+When running in a non-CLI environment the ouput is wrapped around `pre` tags for better formatting.
+
+Use `dbginit` or the flag `USE_VARDUMP` in case you prefer `var_dump`:
+
+```php
+dbginit(['use_vardump' => true]);
+dbg(123);
+// or
+dbg(123, Debug::USE_VARDUMP);
+// which is the same as
+dbg(123, 1);
+```
+
+```
+// Output
+int(123)
+string(8) "a string"
+array(2) {
+  'token' => string(8) "dp83kspo"
+  'is_default' => bool(true)
+}
+```
+
+Use `dbginit` or the flag `USE_HTMLENTITIES` in case you want to encode HTML entities:
+
+```php
+dbginit(['use_htmlentities' => true]);
+dbg('<b>important</b>');
+// or
+dbg('<b>important</b>', Debug::USE_HTMLENTITIES);
+// which is the same as
+dbg('<b>important</b>', 2);
+```
+
+```
+// Output
+&lt;b&gt;important&lt;/b&gt;
+```
+
+### Save debug output in variable
+
+```php
+// dbgr is the same as dbg, except that the output is returned instead of printed.
+$dbg = dbgr(123);
+```
+
+### Log debug output to file
+
+```php
+// dbglog is the same as dbg, except that the output is logged instead of printed.
+dbginit(['log_file' => '/path/to/logfile']);
+dbglog($this->doSomething());
+```
+ 
+ Alternatively you can pass your own monolog logger instance:
+ 
+```php
+$logger = new Logger('channel-name');
+...
+dbginit(['logger' => $logger]);
+dbglog($this->doSomething());
+```
+
+## License
+
+The MIT License (MIT). Please see [License File](https://github.com/fabacino/php-debug-functions/blob/master/LICENSE) for more information.