diff --git a/composer.json b/composer.json
index 32ea2f592..2fc11051f 100644
--- a/composer.json
+++ b/composer.json
@@ -34,8 +34,7 @@
         "psr/http-factory": "^1.0",
         "psr/http-factory-implementation": "^1.0",
         "psr/log": "^1.0|^2.0|^3.0",
-        "symfony/options-resolver": "^3.4.43|^4.4.30|^5.0.11|^6.0",
-        "symfony/polyfill-php80": "^1.17"
+        "symfony/options-resolver": "^3.4.43|^4.4.30|^5.0.11|^6.0"
     },
     "require-dev": {
         "friendsofphp/php-cs-fixer": "^2.19|3.4.*",
diff --git a/src/FrameBuilder.php b/src/FrameBuilder.php
index 5cd61bae6..6fe5f08b0 100644
--- a/src/FrameBuilder.php
+++ b/src/FrameBuilder.php
@@ -74,7 +74,7 @@ public function buildFromBacktraceFrame(string $file, int $line, array $backtrac
         if (isset($backtraceFrame['class']) && isset($backtraceFrame['function'])) {
             $functionName = $backtraceFrame['class'];
 
-            if (str_starts_with($functionName, Frame::ANONYMOUS_CLASS_PREFIX)) {
+            if (mb_substr($functionName, 0, mb_strlen(Frame::ANONYMOUS_CLASS_PREFIX)) === Frame::ANONYMOUS_CLASS_PREFIX) {
                 $functionName = Frame::ANONYMOUS_CLASS_PREFIX . $this->stripPrefixFromFilePath($this->options, substr($backtraceFrame['class'], \strlen(Frame::ANONYMOUS_CLASS_PREFIX)));
             }
 
@@ -107,7 +107,7 @@ private function isFrameInApp(string $file, ?string $functionName): bool
             return false;
         }
 
-        if (null !== $functionName && str_starts_with($functionName, 'Sentry\\')) {
+        if (null !== $functionName && substr($functionName, 0, strlen('Sentry\\')) === 'Sentry\\') {
             return false;
         }
 
@@ -117,7 +117,7 @@ private function isFrameInApp(string $file, ?string $functionName): bool
         $isInApp = true;
 
         foreach ($excludedAppPaths as $excludedAppPath) {
-            if (str_starts_with($absoluteFilePath, $excludedAppPath)) {
+            if (mb_substr($absoluteFilePath, 0, mb_strlen($excludedAppPath)) === $excludedAppPath) {
                 $isInApp = false;
 
                 break;
@@ -125,7 +125,7 @@ private function isFrameInApp(string $file, ?string $functionName): bool
         }
 
         foreach ($includedAppPaths as $includedAppPath) {
-            if (str_starts_with($absoluteFilePath, $includedAppPath)) {
+            if (mb_substr($absoluteFilePath, 0, mb_strlen($includedAppPath)) === $includedAppPath) {
                 $isInApp = true;
 
                 break;
diff --git a/src/Tracing/DynamicSamplingContext.php b/src/Tracing/DynamicSamplingContext.php
index a9ac69ade..c0b3dd39c 100644
--- a/src/Tracing/DynamicSamplingContext.php
+++ b/src/Tracing/DynamicSamplingContext.php
@@ -127,7 +127,7 @@ public static function fromHeader(string $header): self
 
             [$key, $value] = explode('=', $keyValue, 2);
 
-            if (str_starts_with($key, self::SENTRY_ENTRY_PREFIX)) {
+            if (mb_substr($key, 0, mb_strlen(self::SENTRY_ENTRY_PREFIX)) === self::SENTRY_ENTRY_PREFIX) {
                 $samplingContext->set(rawurldecode(mb_substr($key, mb_strlen(self::SENTRY_ENTRY_PREFIX))), rawurldecode($value));
             }
         }
diff --git a/src/Util/PrefixStripper.php b/src/Util/PrefixStripper.php
index 35c261312..d4f24286a 100644
--- a/src/Util/PrefixStripper.php
+++ b/src/Util/PrefixStripper.php
@@ -18,7 +18,7 @@ protected function stripPrefixFromFilePath(?Options $options, string $filePath):
         }
 
         foreach ($options->getPrefixes() as $prefix) {
-            if (str_starts_with($filePath, $prefix)) {
+            if (mb_substr($filePath, 0, mb_strlen($prefix)) === $prefix) {
                 return mb_substr($filePath, mb_strlen($prefix));
             }
         }