Added a documentation for functions

Author: sebprt

README.md

@@ -0,0 +1,26 @@
+# String Expression Language
+This package extends the [ExpressionLanguage](https://symfony.com/doc/current/components/expression_language.html) component of Symfony to compile and evaluate arrays with custom functions.
+
+# Installation
+```
+composer require php-etl/string-expression-language
+```
+
+# Usage
+You can use these expressions in your configuration files as in the following example :
+```yaml
+foo: '@=format("%s", "output")'
+```
+
+# List of available functions
+
+## Generic functions
+* `format(string $format, mixed ...$values) : string` =>  Return a formatted string
+* `trim(string $string, string $characters = " \n\r\t\v\x00") : string` =>  Strip whitespace (or other characters) from the beginning and end of a string
+* `capitalize(string $string) : string` =>  Make a string's first character uppercase
+* `toLowerCase(string $string) : string` => Make a string lowercase
+* `search(string $string, int $offset, ?int $length = null) : string` => Return part of a string
+* `toUpperCase(string $string) : string` => Make a string uppercase
+* `fileName(string $string) : string` => Returns information about a file path
+* `dateTime(string $string) : string` => Returns new DateTimeImmutable object formatted according to the specified format
+* `formatDate(string $string) : string` => Returns date formatted according to given format

src/StringExpressionLanguageProvider.php

@@ -12,10 +12,10 @@ public function getFunctions(): array
         return [
             ExpressionFunction::fromPhp('sprintf', 'format'),
             ExpressionFunction::fromPhp('trim', 'trim'),
-            ExpressionFunction::fromPhp('ucfirst'),
-            ExpressionFunction::fromPhp('strtolower'),
-            ExpressionFunction::fromPhp('substr'),
-            ExpressionFunction::fromPhp('strtoupper'),
+            ExpressionFunction::fromPhp('ucfirst', 'capitalize'),
+            ExpressionFunction::fromPhp('strtolower', 'toLowerCase'),
+            ExpressionFunction::fromPhp('substr', 'search'),
+            ExpressionFunction::fromPhp('strtoupper', 'toUpperCase'),
             new FileName('fileName'),
             new DateTime('dateTime'),
             new FormatDate('formatDate'),