diff --git a/phpseclib/Crypt/Base.php b/phpseclib/Crypt/Base.php
index d015be37..4704a183 100644
--- a/phpseclib/Crypt/Base.php
+++ b/phpseclib/Crypt/Base.php
@@ -1172,7 +1172,7 @@ class Base
      */
     function _encryptBlock($in)
     {
-        user_error((version_compare(PHP_VERSION, '5.0.0', '>=')  ? __METHOD__ : __FUNCTION__)  . '() must extend by class ' . get_class($this), E_USER_ERROR);
+        user_error(__METHOD__ . '() must extend by class ' . __CLASS__, E_USER_ERROR);
     }
 
     /**
@@ -1186,7 +1186,7 @@ class Base
      */
     function _decryptBlock($in)
     {
-        user_error((version_compare(PHP_VERSION, '5.0.0', '>=')  ? __METHOD__ : __FUNCTION__)  . '() must extend by class ' . get_class($this), E_USER_ERROR);
+        user_error(__METHOD__ . '() must extend by class ' . __CLASS__, E_USER_ERROR);
     }
 
     /**
@@ -1201,7 +1201,7 @@ class Base
      */
     function _setupKey()
     {
-        user_error((version_compare(PHP_VERSION, '5.0.0', '>=')  ? __METHOD__ : __FUNCTION__)  . '() must extend by class ' . get_class($this), E_USER_ERROR);
+        user_error(__METHOD__ . '() must extend by class ' . __CLASS__, E_USER_ERROR);
     }
 
     /**
diff --git a/phpseclib/Crypt/RSA.php b/phpseclib/Crypt/RSA.php
index 07f0b967..89862746 100644
--- a/phpseclib/Crypt/RSA.php
+++ b/phpseclib/Crypt/RSA.php
@@ -1454,7 +1454,7 @@ class RSA
      */
     function loadKey($key, $type = false)
     {
-        if (is_object($key) && get_class($key) == 'phpseclib\Crypt\RSA') {
+        if ($key instanceof RSA) {
             $this->privateKeyFormat = $key->privateKeyFormat;
             $this->publicKeyFormat = $key->publicKeyFormat;
             $this->k = $key->k;
diff --git a/phpseclib/File/ASN1.php b/phpseclib/File/ASN1.php
index c4c36ea9..f9355106 100644
--- a/phpseclib/File/ASN1.php
+++ b/phpseclib/File/ASN1.php
@@ -206,7 +206,7 @@ class ASN1
      */
     function decodeBER($encoded)
     {
-        if (is_object($encoded) && get_class($encoded) === 'phpseclib\File\ASN1\Element') {
+        if ($encoded instanceof Element) {
             $encoded = $encoded->element;
         }
 
@@ -779,7 +779,7 @@ class ASN1
      */
     function _encode_der($source, $mapping, $idx = null, $special = array())
     {
-        if (is_object($source) && get_class($source) === 'phpseclib\File\ASN1\Element') {
+        if ($source instanceof Element) {
             return $source->element;
         }
 
@@ -997,7 +997,7 @@ class ASN1
                     case !isset($source):
                         return $this->_encode_der(null, array('type' => self::TYPE_NULL) + $mapping, null, $special);
                     case is_int($source):
-                    case $source instanceof \phpseclib\Math\BigInteger:
+                    case $source instanceof BigInteger:
                         return $this->_encode_der($source, array('type' => self::TYPE_INTEGER) + $mapping, null, $special);
                     case is_float($source):
                         return $this->_encode_der($source, array('type' => self::TYPE_REAL) + $mapping, null, $special);
diff --git a/phpseclib/File/X509.php b/phpseclib/File/X509.php
index 88b1f985..7f1b2f81 100644
--- a/phpseclib/File/X509.php
+++ b/phpseclib/File/X509.php
@@ -3601,25 +3601,24 @@ class X509
      */
     function _sign($key, $signatureAlgorithm)
     {
-        switch (get_class($key)) {
-            case 'phpseclib\Crypt\RSA':
-                switch ($signatureAlgorithm) {
-                    case 'md2WithRSAEncryption':
-                    case 'md5WithRSAEncryption':
-                    case 'sha1WithRSAEncryption':
-                    case 'sha224WithRSAEncryption':
-                    case 'sha256WithRSAEncryption':
-                    case 'sha384WithRSAEncryption':
-                    case 'sha512WithRSAEncryption':
-                        $key->setHash(preg_replace('#WithRSAEncryption$#', '', $signatureAlgorithm));
-                        $key->setSignatureMode(RSA::SIGNATURE_PKCS1);
+        if ($key instanceof RSA) {
+            switch ($signatureAlgorithm) {
+                case 'md2WithRSAEncryption':
+                case 'md5WithRSAEncryption':
+                case 'sha1WithRSAEncryption':
+                case 'sha224WithRSAEncryption':
+                case 'sha256WithRSAEncryption':
+                case 'sha384WithRSAEncryption':
+                case 'sha512WithRSAEncryption':
+                    $key->setHash(preg_replace('#WithRSAEncryption$#', '', $signatureAlgorithm));
+                    $key->setSignatureMode(RSA::SIGNATURE_PKCS1);
 
-                        $this->currentCert['signature'] = base64_encode("\0" . $key->sign($this->signatureSubject));
-                        return $this->currentCert;
-                }
-            default:
-                return false;
+                    $this->currentCert['signature'] = base64_encode("\0" . $key->sign($this->signatureSubject));
+                    return $this->currentCert;
+            }
         }
+
+        return false;
     }
 
     /**
@@ -4162,7 +4161,7 @@ class X509
                 return $this->computeKeyIdentifier($key['certificationRequestInfo']['subjectPKInfo']['subjectPublicKey'], $method);
             case !is_object($key):
                 return false;
-            case get_class($key) === 'phpseclib\File\ASN1\Element':
+            case $key instanceof Element:
                 // Assume the element is a bitstring-packed key.
                 $asn1 = new ASN1();
                 $decoded = $asn1->decodeBER($key->element);
@@ -4184,7 +4183,7 @@ class X509
                 }
                 $key = $raw;    // Is a public key.
                 break;
-            case get_class($key) === 'phpseclib\File\X509':
+            case $key instanceof X509:
                 if (isset($key->publicKey)) {
                     return $this->computeKeyIdentifier($key->publicKey, $method);
                 }
@@ -4223,22 +4222,17 @@ class X509
      */
     function _formatSubjectPublicKey()
     {
-        if (!isset($this->publicKey) || !is_object($this->publicKey)) {
-            return false;
+        if ($this->publicKey instanceof RSA) {
+            // the following two return statements do the same thing. i dunno.. i just prefer the later for some reason.
+            // the former is a good example of how to do fuzzing on the public key
+            //return new Element(base64_decode(preg_replace('#-.+-|[\r\n]#', '', $this->publicKey->getPublicKey())));
+            return array(
+                'algorithm' => array('algorithm' => 'rsaEncryption'),
+                'subjectPublicKey' => $this->publicKey->getPublicKey(RSA::PUBLIC_FORMAT_PKCS1)
+            );
         }
 
-        switch (get_class($this->publicKey)) {
-            case 'phpseclib\Crypt\RSA':
-                // the following two return statements do the same thing. i dunno.. i just prefer the later for some reason.
-                // the former is a good example of how to do fuzzing on the public key
-                //return new Element(base64_decode(preg_replace('#-.+-|[\r\n]#', '', $this->publicKey->getPublicKey())));
-                return array(
-                    'algorithm' => array('algorithm' => 'rsaEncryption'),
-                    'subjectPublicKey' => $this->publicKey->getPublicKey(RSA::PUBLIC_FORMAT_PKCS1)
-                );
-            default:
-                return false;
-        }
+        return false;
     }
 
     /**
diff --git a/phpseclib/Math/BigInteger.php b/phpseclib/Math/BigInteger.php
index 1f0994a0..9d96fc16 100644
--- a/phpseclib/Math/BigInteger.php
+++ b/phpseclib/Math/BigInteger.php
@@ -332,7 +332,7 @@ class BigInteger
                 switch (true) {
                     case is_resource($x) && get_resource_type($x) == 'GMP integer':
                     // PHP 5.6 switched GMP from using resources to objects
-                    case is_object($x) && get_class($x) == 'GMP':
+                    case $x instanceof \GMP:
                         $this->value = $x;
                         return;
                 }
diff --git a/phpseclib/Net/SCP.php b/phpseclib/Net/SCP.php
index 79bf30dc..18c8bbc5 100644
--- a/phpseclib/Net/SCP.php
+++ b/phpseclib/Net/SCP.php
@@ -110,22 +110,15 @@ class SCP
      */
     function __construct($ssh)
     {
-        if (!is_object($ssh)) {
+        if ($ssh instanceof SSH2) {
+            $this->mode = self::MODE_SSH2;
+        } elseif ($ssh instanceof SSH1) {
+            $this->packet_size = 50000;
+            $this->mode = self::MODE_SSH1;
+        } else {
             return;
         }
 
-        switch (get_class($ssh)) {
-            case 'phpseclib\Net\SSH2':
-                $this->mode = self::MODE_SSH2;
-                break;
-            case 'phpseclib\Net\SSH1':
-                $this->packet_size = 50000;
-                $this->mode = self::MODE_SSH1;
-                break;
-            default:
-                return;
-        }
-
         $this->ssh = $ssh;
     }
 
diff --git a/phpseclib/Net/SFTP/Stream.php b/phpseclib/Net/SFTP/Stream.php
index bb7dce3d..3fa5aa50 100644
--- a/phpseclib/Net/SFTP/Stream.php
+++ b/phpseclib/Net/SFTP/Stream.php
@@ -17,6 +17,7 @@
 
 namespace phpseclib\Net\SFTP;
 
+use phpseclib\Crypt\RSA;
 use phpseclib\Net\SFTP;
 
 /**
@@ -169,7 +170,7 @@ class Stream
         if ($host[0] == '$') {
             $host = substr($host, 1);
             global $$host;
-            if (!is_object($$host) || get_class($$host) != 'phpseclib\Net\SFTP') {
+            if (($$host instanceof SFTP) === false) {
                 return false;
             }
             $this->sftp = $$host;
@@ -183,7 +184,7 @@ class Stream
             if (isset($context[$scheme]['sftp'])) {
                 $sftp = $context[$scheme]['sftp'];
             }
-            if (isset($sftp) && is_object($sftp) && get_class($sftp) == 'phpseclib\Net\SFTP') {
+            if (isset($sftp) && $sftp instanceof SFTP) {
                 $this->sftp = $sftp;
                 return $path;
             }
@@ -193,7 +194,7 @@ class Stream
             if (isset($context[$scheme]['password'])) {
                 $pass = $context[$scheme]['password'];
             }
-            if (isset($context[$scheme]['privkey']) && is_object($context[$scheme]['privkey']) && get_class($context[$scheme]['privkey']) == 'phpseclib\Crypt\RSA') {
+            if (isset($context[$scheme]['privkey']) && $context[$scheme]['privkey'] instanceof RSA) {
                 $pass = $context[$scheme]['privkey'];
             }
 
diff --git a/phpseclib/Net/SSH2.php b/phpseclib/Net/SSH2.php
index 9cf93f5b..6198afc8 100644
--- a/phpseclib/Net/SSH2.php
+++ b/phpseclib/Net/SSH2.php
@@ -59,6 +59,7 @@ use phpseclib\Crypt\RSA;
 use phpseclib\Crypt\TripleDES;
 use phpseclib\Crypt\Twofish;
 use phpseclib\Math\BigInteger; // Used to do Diffie-Hellman key exchange and DSA/RSA signature verification.
+use phpseclib\System\SSH\Agent;
 
 /**
  * Pure-PHP implementation of SSHv2.
@@ -1805,13 +1806,10 @@ class SSH2
             return !is_string($password) && !is_array($password) ? false : $this->_keyboard_interactive_process($password);
         }
 
-        if (is_object($password)) {
-            switch (get_class($password)) {
-                case 'phpseclib\Crypt\RSA':
-                    return $this->_privatekey_login($username, $password);
-                case 'phpseclib\System\SSH\Agent':
-                    return $this->_ssh_agent_login($username, $password);
-            }
+        if ($password instanceof RSA) {
+            return $this->_privatekey_login($username, $password);
+        } elseif ($password instanceof Agent) {
+            return $this->_ssh_agent_login($username, $password);
         }
 
         if (is_array($password)) {