Fix misc stuff

Author: defuse

README.md

@@ -16,8 +16,7 @@ requires PHP 5.6 or newer and OpenSSL 1.0.1 or newer.** We recommend using a
 version of PHP that [still has security
 support](https://www.php.net/supported-versions.php), which at the time of
 writing means PHP 7.3 or later. Using this library with an unsupported
-version of PHP could lead to security vulnerabilities. This library is not
-currently tested against PHP 8.0.
+version of PHP could lead to security vulnerabilities.
 
 The current version of `php-encryption` is v2.3. This library is expected to
 remain stable and supported by its authors with security and bugfixes until at

src/File.php

@@ -191,6 +191,9 @@ public static function decryptResourceWithPassword($inputHandle, $outputHandle,
      */
     private static function encryptFileInternal($inputFilename, $outputFilename, KeyOrPassword $secret)
     {
+        if (realpath($inputFilename) === realpath($outputFilename)) {
+            throw new Ex\IOException('Input and output filenames must be different.');
+        }
         /* Open the input file. */
         $if = @\fopen($inputFilename, 'rb');
         if ($if === false) {
@@ -256,6 +259,10 @@ private static function encryptFileInternal($inputFilename, $outputFilename, Key
      */
     private static function decryptFileInternal($inputFilename, $outputFilename, KeyOrPassword $secret)
     {
+        if (realpath($inputFilename) === realpath($outputFilename)) {
+            throw new Ex\IOException('Input and output filenames must be different.');
+        }
+
         /* Open the input file. */
         $if = @\fopen($inputFilename, 'rb');
         if ($if === false) {

test/unit/CoreTest.php

@@ -80,7 +80,7 @@ public function testOurSubstrOutOfBorders()
 
         // We want to be like substr, so confirm that behavior.
         if (PHP_VERSION_ID < 80000) {
-            // In PHP 8.0, substr starts returning '' instead of the empty string.
+            // In PHP 8.0, substr starts returning '' instead of false.
             // Core::ourSubstr should behave the OLD way.
             $this->assertSame(
                 false,