Create a new expression to get file extension

src/FileExtension.php

@@ -0,0 +1,37 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Kiboko\Component\StringExpressionLanguage;
+
+use Symfony\Component\ExpressionLanguage\ExpressionFunction;
+
+final class FileExtension extends ExpressionFunction
+{
+    public function __construct($name)
+    {
+        parent::__construct(
+            $name,
+            $this->compile(...)->bindTo($this),
+            $this->evaluate(...)->bindTo($this)
+        );
+    }
+
+    private function compile(string $value): string
+    {
+        return <<<PHP
+            (function () use (\$input) : string {
+                \$parts = explode('.', basename($value));
+
+                return end(\$parts);
+            })()
+            PHP;
+    }
+
+    private function evaluate(array $context, string $imageUrl): string
+    {
+        $parts = explode('.', basename($imageUrl));
+
+        return end($parts);
+    }
+}

src/StringExpressionLanguageProvider.php

@@ -38,6 +38,7 @@ public function getFunctions(): array
             new AsInteger('asInteger'),
             new AsString('asString'),
             new Slugify('slugify'),
+            new FileExtension('fileExtension'),
         ];
     }
 }