README.md

@@ -257,6 +257,11 @@ One or more environment variables failed assertions: SESSION_STORE is not an
 allowed value
 ```
 
+It is also possible to define a regex that your environment variable should be.
+```php
+$dotenv->required('FOO')->allowedRegexValues('([[:lower:]]{3})');
+```
+
 ### Comments
 
 You can comment your `.env` file using the `#` character. E.g.

composer.json

@@ -21,7 +21,7 @@
         "symfony/polyfill-ctype": "^1.9"
     },
     "require-dev": {
-        "phpunit/phpunit": "^4.8.35 || ^5.0 || ^6.0"
+        "phpunit/phpunit": "^4.8.35 || ^5.0 || ^6.0 || ^7.0"
     },
     "autoload": {
         "psr-4": {
@@ -30,7 +30,7 @@
     },
     "extra": {
         "branch-alias": {
-            "dev-master": "3.5-dev"
+            "dev-master": "3.6-dev"
         }
     }
 }

src/Regex/Regex.php

@@ -6,6 +6,21 @@
 
 class Regex
 {
+    /**
+     * Perform a preg match, wrapping up the result.
+     *
+     * @param string $pattern
+     * @param string $subject
+     *
+     * @return \Dotenv\Regex\Result
+     */
+    public static function match($pattern, $subject)
+    {
+        return self::pregAndWrap(function ($subject) use ($pattern) {
+            return (int) @preg_match($pattern, $subject);
+        }, $subject);
+    }
+
     /**
      * Perform a preg replace, wrapping up the result.
      *
@@ -18,7 +33,7 @@ class Regex
     public static function replace($pattern, $replacement, $subject)
     {
         return self::pregAndWrap(function ($subject) use ($pattern, $replacement) {
-            return preg_replace($pattern, $replacement, $subject);
+            return (string) @preg_replace($pattern, $replacement, $subject);
         }, $subject);
     }
 
@@ -34,7 +49,7 @@ public static function replace($pattern, $replacement, $subject)
     public static function replaceCallback($pattern, callable $callback, $subject)
     {
         return self::pregAndWrap(function ($subject) use ($pattern, $callback) {
-            return preg_replace_callback($pattern, $callback, $subject);
+            return (string) @preg_replace_callback($pattern, $callback, $subject);
         }, $subject);
     }
 
@@ -48,7 +63,7 @@ public static function replaceCallback($pattern, callable $callback, $subject)
      */
     private static function pregAndWrap(callable $operation, $subject)
     {
-        $result = (string) @$operation($subject);
+        $result = $operation($subject);
 
         if (($e = preg_last_error()) !== PREG_NO_ERROR) {
             return Error::create(self::lookupError($e));

src/Regex/Result.php

@@ -14,7 +14,7 @@ abstract public function success();
     /**
      * Get the error value, if possible.
      *
-     * @return string
+     * @return string|int
      */
     public function getSuccess()
     {

src/Regex/Success.php

@@ -8,14 +8,14 @@
 class Success extends Result
 {
     /**
-     * @var string
+     * @var string|int
      */
     private $value;
 
     /**
      * Internal constructor for a success value.
      *
-     * @param string $value
+     * @param string|int $value
      *
      * @return void
      */
@@ -27,7 +27,7 @@ private function __construct($value)
     /**
      * Create a new success value.
      *
-     * @param string $value
+     * @param string|int $value
      *
      * @return \Dotenv\Regex\Result
      */

src/Validator.php

@@ -3,6 +3,7 @@
 namespace Dotenv;
 
 use Dotenv\Exception\ValidationException;
+use Dotenv\Regex\Regex;
 
 /**
  * This is the validator class.
@@ -138,6 +139,30 @@ function ($value) use ($choices) {
         );
     }
 
+    /**
+     * Assert that each variable matches the given regular expression.
+     *
+     * @param string $regex
+     *
+     * @throws \Dotenv\Exception\ValidationException
+     *
+     * @return \Dotenv\Validator
+     */
+    public function allowedRegexValues($regex)
+    {
+        return $this->assertCallback(
+            function ($value) use ($regex)
+            {
+                if ($value === null) {
+                    return true;
+                }
+
+                return Regex::match($regex, $value)->success()->getOrElse(0) === 1;
+            },
+            sprintf('does not match "%s"' , $regex)
+        );
+    }
+
     /**
      * Assert that the callback returns true for each variable.
      *

tests/Dotenv/ValidatorTest.php

@@ -408,4 +408,42 @@ public function testIfPresentIntegerNonExist()
         $dotenv->ifPresent(['VAR_DOES_NOT_EXIST_234782462764'])->isInteger();
         $this->assertTrue(true);
     }
+
+    public function testDotenvRegexMatchPass()
+    {
+        $dotenv = Dotenv::create($this->fixturesFolder);
+        $dotenv->load();
+        $dotenv->required('FOO')->allowedRegexValues('([[:lower:]]{3})');
+        $this->assertTrue(true);
+    }
+
+    /**
+     * @expectedException \Dotenv\Exception\ValidationException
+     * @expectedExceptionMessage One or more environment variables failed assertions: FOO does not match "/^([[:lower:]]{1})$/".
+     */
+    public function testDotenvRegexMatchFail()
+    {
+        $dotenv = Dotenv::create($this->fixturesFolder);
+        $dotenv->load();
+        $dotenv->required('FOO')->allowedRegexValues('/^([[:lower:]]{1})$/');
+    }
+
+    /**
+     * @expectedException \Dotenv\Exception\ValidationException
+     * @expectedExceptionMessage One or more environment variables failed assertions: FOO does not match "/([[:lower:]{1{".
+     */
+    public function testDotenvRegexMatchError()
+    {
+        $dotenv = Dotenv::create($this->fixturesFolder);
+        $dotenv->load();
+        $dotenv->required('FOO')->allowedRegexValues('/([[:lower:]{1{');
+    }
+
+    public function testDotenvRegexMatchNotPresent()
+    {
+        $dotenv = Dotenv::create($this->fixturesFolder);
+        $dotenv->load();
+        $dotenv->ifPresent('FOOOOOOOOOOO')->allowedRegexValues('([[:lower:]]{3})');
+        $this->assertTrue(true);
+    }
 }