add preg_match expression

src/DateTime.php

@@ -24,7 +24,7 @@ private function compile(string $date, string $format, string $timezone = 'null'
             PHP;
     }
 
-    private function evaluate(array $context, string $date, string $format, string $timezone = null)
+    private function evaluate(array $context, string $date, string $format, ?string $timezone = null)
     {
         return \DateTimeImmutable::createFromFormat($format, $date, null !== $timezone ? new \DateTimeZone($timezone) : null);
     }

src/Now.php

@@ -17,14 +17,14 @@ public function __construct($name)
         );
     }
 
-    private function compile(string $timezone = null): string
+    private function compile(?string $timezone = null): string
     {
         return <<<PHP
                 (new \\DateTime('now', {$timezone} !== null ? new \\DateTimeZone({$timezone}) : null))
             PHP;
     }
 
-    private function evaluate(array $context, string $timezone = null)
+    private function evaluate(array $context, ?string $timezone = null)
     {
         return new \DateTime('now', null !== $timezone ? new \DateTimeZone($timezone) : null);
     }

src/StringExpressionLanguageProvider.php

@@ -24,6 +24,7 @@ public function getFunctions(): array
             ExpressionFunction::fromPhp('strip_tags', 'stripHtml'),
             ExpressionFunction::fromPhp('json_decode', 'decode'),
             ExpressionFunction::fromPhp('preg_replace', 'replaceByExpression'),
+            new TestPattern('testPattern'),
             new CapitalizeWords('capitalizeWords'),
             ExpressionFunction::fromPhp('rtrim', 'removeWhitespaces'),
             ExpressionFunction::fromPhp('explode', 'splitIntoArray'),

src/TestPattern.php

@@ -0,0 +1,41 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Kiboko\Component\StringExpressionLanguage;
+
+use Symfony\Component\ExpressionLanguage\ExpressionFunction;
+
+class TestPattern extends ExpressionFunction
+{
+    public function __construct($name)
+    {
+        parent::__construct(
+            $name,
+            $this->compile(...)->bindTo($this),
+            $this->evaluate(...)->bindTo($this)
+        );
+    }
+
+    private function compile(string $pattern, string $subject): string
+    {
+        return <<<PHP
+                \$result = preg_match({$pattern}, {$subject});
+                if (!\$result) {
+                    return false;
+                } else {
+                    return true;
+                }
+            PHP;
+    }
+
+    private function evaluate(array $context, string $pattern, string $subject): bool
+    {
+        $result = preg_match($pattern, $subject);
+        if (!$result) {
+            return false;
+        }
+
+        return true;
+    }
+}