diff --git a/build/controllers/PhpDocController.php b/build/controllers/PhpDocController.php
index dca2156b61..c31270101d 100644
--- a/build/controllers/PhpDocController.php
+++ b/build/controllers/PhpDocController.php
@@ -170,7 +170,7 @@ class PhpDocController extends Controller
         $namespaceLine = '';
         $contentAfterNamespace = false;
         foreach($lines as $i => $line) {
-            if (substr(trim($line), 0, 9) === 'namespace') {
+            if (substr_compare(trim($line), 'namespace', 0, 9) === 0) {
                 $namespace = $i;
                 $namespaceLine = trim($line);
             } elseif ($namespace !== false && trim($line) !== '') {
@@ -275,13 +275,13 @@ class PhpDocController extends Controller
 
         // TODO move these checks to different action
         $lines = explode("\n", $newDoc);
-        if (trim($lines[1]) == '*' || substr(trim($lines[1]), 0, 3) == '* @') {
+        if (trim($lines[1]) == '*' || substr_compare(trim($lines[1]), '* @', 0, 3) === 0) {
             $this->stderr("[WARN] Class $className has no short description.\n", Console::FG_YELLOW, Console::BOLD);
         }
         foreach ($lines as $line) {
-            if (substr(trim($line), 0, 9) == '* @since ') {
+            if (substr_compare(trim($line), '* @since ', 0, 9) === 0) {
                 $seenSince = true;
-            } elseif (substr(trim($line), 0, 10) == '* @author ') {
+            } elseif (substr_compare(trim($line), '* @author ', 0, 10) === 0) {
                 $seenAuthor = true;
             }
         }
@@ -350,13 +350,13 @@ class PhpDocController extends Controller
         $propertyPart = false;
         $propertyPosition = false;
         foreach ($lines as $i => $line) {
-            if (substr(trim($line), 0, 12) == '* @property ') {
+            if (substr_compare(trim($line), '* @property ', 0, 12) === 0) {
                 $propertyPart = true;
             } elseif ($propertyPart && trim($line) == '*') {
                 $propertyPosition = $i;
                 $propertyPart = false;
             }
-            if (substr(trim($line), 0, 10) == '* @author ' && $propertyPosition === false) {
+            if (substr_compare(trim($line), '* @author ', 0, 10) === 0 && $propertyPosition === false) {
                 $propertyPosition = $i - 1;
                 $propertyPart = false;
             }
diff --git a/extensions/apidoc/models/TypeDoc.php b/extensions/apidoc/models/TypeDoc.php
index 12bbc5753c..80d31d91ee 100644
--- a/extensions/apidoc/models/TypeDoc.php
+++ b/extensions/apidoc/models/TypeDoc.php
@@ -46,7 +46,7 @@ class TypeDoc extends BaseDoc
                 }
             }
         }
-        if (substr($subjectName, -2, 2) == '()') {
+        if (substr_compare($subjectName, '()', -2, 2) === 0) {
             return null;
         }
         if ($this->properties === null) {
diff --git a/extensions/apidoc/renderers/BaseRenderer.php b/extensions/apidoc/renderers/BaseRenderer.php
index 86ab186d0b..812cfd924a 100644
--- a/extensions/apidoc/renderers/BaseRenderer.php
+++ b/extensions/apidoc/renderers/BaseRenderer.php
@@ -72,7 +72,7 @@ abstract class BaseRenderer extends Component
         foreach ($types as $type) {
             $postfix = '';
             if (!is_object($type)) {
-                if (substr($type, -2, 2) == '[]') {
+                if (substr_compare($type, '[]', -2, 2) === 0) {
                     $postfix = '[]';
                     $type = substr($type, 0, -2);
                 }
diff --git a/extensions/apidoc/templates/html/views/seeAlso.php b/extensions/apidoc/templates/html/views/seeAlso.php
index 5d6e3774c5..12d83c12fc 100644
--- a/extensions/apidoc/templates/html/views/seeAlso.php
+++ b/extensions/apidoc/templates/html/views/seeAlso.php
@@ -23,7 +23,7 @@ if (empty($see)) {
 } else {
     echo '<p>See also:</p><ul>';
     foreach ($see as $ref) {
-        if (substr($ref, -1, 1) != '>') {
+        if (substr_compare($ref, '>', -1, 1)) {
             $ref .= '.';
         }
         echo "<li>$ref</li>";
diff --git a/extensions/authclient/OAuth1.php b/extensions/authclient/OAuth1.php
index 2d7841010d..356a71b3a3 100644
--- a/extensions/authclient/OAuth1.php
+++ b/extensions/authclient/OAuth1.php
@@ -349,7 +349,7 @@ class OAuth1 extends BaseOAuth
             $headerParams[] = 'realm="' . rawurlencode($realm) . '"';
         }
         foreach ($params as $key => $value) {
-            if (substr($key, 0, 5) != 'oauth') {
+            if (substr_compare($key, 'oauth', 0, 5)) {
                 continue;
             }
             $headerParams[] = rawurlencode($key) . '="' . rawurlencode($value) . '"';
diff --git a/extensions/authclient/OpenId.php b/extensions/authclient/OpenId.php
index b26e5fe619..27839d7204 100644
--- a/extensions/authclient/OpenId.php
+++ b/extensions/authclient/OpenId.php
@@ -761,7 +761,7 @@ class OpenId extends BaseClient implements ClientInterface
         } else {
             // 'ax' prefix is either undefined, or points to another extension, so we search for another prefix
             foreach ($this->data as $key => $value) {
-                if (substr($key, 0, strlen('openid_ns_')) == 'openid_ns_' && $value == 'http://openid.net/srv/ax/1.0') {
+                if (substr_compare($key, 'openid_ns_', 0, 10) === 0  && $value == 'http://openid.net/srv/ax/1.0') {
                     $alias = substr($key, strlen('openid_ns_'));
                     break;
                 }
@@ -775,7 +775,7 @@ class OpenId extends BaseClient implements ClientInterface
         $attributes = [];
         foreach ($this->data as $key => $value) {
             $keyMatch = 'openid_' . $alias . '_value_';
-            if (substr($key, 0, strlen($keyMatch)) != $keyMatch) {
+            if (substr_compare($key, $keyMatch, 0, strlen($keyMatch))) {
                 continue;
             }
             $key = substr($key, strlen($keyMatch));
@@ -802,7 +802,7 @@ class OpenId extends BaseClient implements ClientInterface
         $sregToAx = array_flip($this->axToSregMap);
         foreach ($this->data as $key => $value) {
             $keyMatch = 'openid_sreg_';
-            if (substr($key, 0, strlen($keyMatch)) != $keyMatch) {
+            if (substr_compare($key, $keyMatch, 0, strlen($keyMatch))) {
                 continue;
             }
             $key = substr($key, strlen($keyMatch));
diff --git a/extensions/gii/generators/model/Generator.php b/extensions/gii/generators/model/Generator.php
index 534dfe6cb9..aeb168a81a 100644
--- a/extensions/gii/generators/model/Generator.php
+++ b/extensions/gii/generators/model/Generator.php
@@ -478,7 +478,7 @@ class Generator extends \yii\gii\Generator
         if ($this->isReservedKeyword($this->modelClass)) {
             $this->addError('modelClass', 'Class name cannot be a reserved PHP keyword.');
         }
-        if (substr($this->tableName, -1) !== '*' && $this->modelClass == '') {
+        if (substr_compare($this->tableName, '*', -1) && $this->modelClass == '') {
             $this->addError('modelClass', 'Model Class cannot be blank if table name does not end with asterisk.');
         }
     }
diff --git a/extensions/gii/generators/module/Generator.php b/extensions/gii/generators/module/Generator.php
index 353afe67cd..270454865c 100644
--- a/extensions/gii/generators/module/Generator.php
+++ b/extensions/gii/generators/module/Generator.php
@@ -146,7 +146,7 @@ EOD;
         if (strpos($this->moduleClass, '\\') === false || Yii::getAlias('@' . str_replace('\\', '/', $this->moduleClass), false) === false) {
             $this->addError('moduleClass', 'Module class must be properly namespaced.');
         }
-        if (substr($this->moduleClass, -1, 1) == '\\') {
+        if (substr_compare($this->moduleClass, '\\', -1, 1) === 0) {
             $this->addError('moduleClass', 'Module class name must not be empty. Please enter a fully qualified class name. e.g. "app\\modules\\admin\\Module".');
         }
     }
diff --git a/extensions/sphinx/gii/model/Generator.php b/extensions/sphinx/gii/model/Generator.php
index 07664db2bb..c7fb10ef5f 100644
--- a/extensions/sphinx/gii/model/Generator.php
+++ b/extensions/sphinx/gii/model/Generator.php
@@ -266,7 +266,7 @@ class Generator extends \yii\gii\Generator
         if ($this->isReservedKeyword($this->modelClass)) {
             $this->addError('modelClass', 'Class name cannot be a reserved PHP keyword.');
         }
-        if (substr($this->indexName, -1) !== '*' && $this->modelClass == '') {
+        if (substr_compare($this->indexName, '*', -1) && $this->modelClass == '') {
             $this->addError('modelClass', 'Model Class cannot be blank if table name does not end with asterisk.');
         }
     }
diff --git a/framework/console/controllers/MessageController.php b/framework/console/controllers/MessageController.php
index 519a09bfe2..0f03d03f42 100644
--- a/framework/console/controllers/MessageController.php
+++ b/framework/console/controllers/MessageController.php
@@ -333,7 +333,7 @@ class MessageController extends Controller
             ksort($translated);
             foreach ($translated as $message => $translation) {
                 if (!isset($merged[$message]) && !isset($todo[$message]) && !$removeUnused) {
-                    if (substr($translation, 0, 2) === '@@' && substr($translation, -2) === '@@') {
+                    if (substr_compare($translation, '@@', 0, 2) === 0 && substr_compare($translation, '@@', -2) === 0) {
                         $todo[$message] = $translation;
                     } else {
                         $todo[$message] = '@@' . $translation . '@@';
diff --git a/framework/grid/CheckboxColumn.php b/framework/grid/CheckboxColumn.php
index ddb30dbf1c..531710aa0f 100644
--- a/framework/grid/CheckboxColumn.php
+++ b/framework/grid/CheckboxColumn.php
@@ -63,7 +63,7 @@ class CheckboxColumn extends Column
         if (empty($this->name)) {
             throw new InvalidConfigException('The "name" property must be set.');
         }
-        if (substr($this->name, -2) !== '[]') {
+        if (substr_compare($this->name, '[]', -2)) {
             $this->name .= '[]';
         }
     }
diff --git a/framework/helpers/BaseHtml.php b/framework/helpers/BaseHtml.php
index 0e3dc82eff..204ab041eb 100644
--- a/framework/helpers/BaseHtml.php
+++ b/framework/helpers/BaseHtml.php
@@ -803,7 +803,7 @@ class BaseHtml
         $options['name'] = $name;
         if (isset($options['unselect'])) {
             // add a hidden field so that if the list box has no option being selected, it still submits a value
-            if (substr($name, -2) === '[]') {
+            if (substr_compare($name, '[]', -2) === 0) {
                 $name = substr($name, 0, -2);
             }
             $hidden = static::hiddenInput($name, $options['unselect']);
diff --git a/framework/web/UrlManager.php b/framework/web/UrlManager.php
index 3aeb23fba1..4d484696ba 100644
--- a/framework/web/UrlManager.php
+++ b/framework/web/UrlManager.php
@@ -238,7 +238,7 @@ class UrlManager extends Component
             $suffix = (string) $this->suffix;
             if ($suffix !== '' && $pathInfo !== '') {
                 $n = strlen($this->suffix);
-                if (substr($pathInfo, -$n) === $this->suffix) {
+                if (substr_compare($pathInfo, $this->suffix, -$n) === 0) {
                     $pathInfo = substr($pathInfo, 0, -$n);
                     if ($pathInfo === '') {
                         // suffix alone is not allowed
diff --git a/framework/web/UrlRule.php b/framework/web/UrlRule.php
index fdb0ddf3e7..18d5d32484 100644
--- a/framework/web/UrlRule.php
+++ b/framework/web/UrlRule.php
@@ -215,7 +215,7 @@ class UrlRule extends Object implements UrlRuleInterface
         $suffix = (string) ($this->suffix === null ? $manager->suffix : $this->suffix);
         if ($suffix !== '' && $pathInfo !== '') {
             $n = strlen($suffix);
-            if (substr($pathInfo, -$n) === $suffix) {
+            if (substr_compare($pathInfo, $suffix, -$n) === 0) {
                 $pathInfo = substr($pathInfo, 0, -$n);
                 if ($pathInfo === '') {
                     // suffix alone is not allowed