From 452f19ee8391c8d272635254a4dabbe702327d2a Mon Sep 17 00:00:00 2001
From: Paragon Initiative Enterprises <security@paragonie.com>
Date: Fri, 29 Jul 2016 12:20:38 -0400
Subject: [PATCH] 1.5.x - Proposed fix to work around
 https://github.com/stefanesser/suhosin/issues/92

See #39
---
 src/Asymmetric/Crypto.php | 4 ++--
 src/Util.php              | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/Asymmetric/Crypto.php b/src/Asymmetric/Crypto.php
index 47adc91..cc5dd27 100644
--- a/src/Asymmetric/Crypto.php
+++ b/src/Asymmetric/Crypto.php
@@ -166,7 +166,7 @@ public static function seal(
                 'Argument 2: Expected an instance of EncryptionPublicKey'
             );
         }
-        if (!function_exists('\\Sodium\\crypto_box_seal')) {
+        if (!\is_callable('\\Sodium\\crypto_box_seal')) {
             throw new CryptoException\CannotPerformOperation(
                 'crypto_box_seal is not available'
             );
@@ -247,7 +247,7 @@ public static function unseal(
         if (!$raw) {
             $source = \Sodium\hex2bin($source);
         }
-        if (!function_exists('\\Sodium\\crypto_box_seal_open')) {
+        if (!\is_callable('\\Sodium\\crypto_box_seal_open')) {
             throw new CryptoException\CannotPerformOperation(
                 'crypto_box_seal_open is not available, please update/reinstall libsodium'
             );
diff --git a/src/Util.php b/src/Util.php
index 01bb215..05515f9 100644
--- a/src/Util.php
+++ b/src/Util.php
@@ -86,7 +86,7 @@ public static function safeStrlen($str)
     {
         static $exists = null;
         if ($exists === null) {
-            $exists = \function_exists('mb_strlen');
+            $exists = \is_callable('mb_strlen');
         }
         if (!\is_string($str)) {
             throw new Alerts\InvalidType(
@@ -125,7 +125,7 @@ public static function safeSubstr($str, $start, $length = null)
     {
         static $exists = null;
         if ($exists === null) {
-            $exists = \function_exists('mb_substr');
+            $exists = \is_callable('mb_substr');
         }
         if ($exists) {
             // mb_substr($str, 0, NULL, '8bit') returns an empty string on PHP