diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPhpCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPhpCodegen.java
index 35a411d708ae..81068295053d 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPhpCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPhpCodegen.java
@@ -69,6 +69,7 @@ public abstract class AbstractPhpCodegen extends DefaultCodegen implements Codeg
     protected String interfaceNamePrefix = "", interfaceNameSuffix = "Interface";
     protected String abstractNamePrefix = "Abstract", abstractNameSuffix = "";
     protected String traitNamePrefix = "", traitNameSuffix = "Trait";
+    protected boolean declareStrictTypes = false;
 
     private Map<String, String> schemaKeyToModelNameCache = new HashMap<>();
 
@@ -285,6 +286,11 @@ public void processOpts() {
 
         // all PHP codegens requires Composer, it means that we need to exclude from SVN at least vendor folder
         supportingFiles.add(new SupportingFile("gitignore", "", ".gitignore"));
+        // Add declareStrictTypes property to the additionalProperties
+    if (additionalProperties.containsKey("declareStrictTypes")) {
+        this.declareStrictTypes = Boolean.parseBoolean(additionalProperties.get("declareStrictTypes").toString());
+    }
+    additionalProperties.put("declareStrictTypes", declareStrictTypes);
     }
 
     public String toSrcPath(final String packageName, final String basePath) {
@@ -567,6 +573,14 @@ public String toInterfaceName(final String name) {
     public String toAbstractName(final String name) {
         return camelize(abstractNamePrefix + name + abstractNameSuffix);
     }
+    
+@Override
+public String getHelp() {
+    return "Generates a PHP client library." + "\n" +
+           "Options:\n" +
+           "  - declareStrictTypes: boolean, set to true to add declare(strict_types=1); in generated PHP files.";
+}
+
 
     /**
      * Output the proper trait name (capitalized).
diff --git a/modules/openapi-generator/src/main/resources/php/ApiException.mustache b/modules/openapi-generator/src/main/resources/php/ApiException.mustache
index 285839e2ded7..46c78766fdf1 100644
--- a/modules/openapi-generator/src/main/resources/php/ApiException.mustache
+++ b/modules/openapi-generator/src/main/resources/php/ApiException.mustache
@@ -1,4 +1,6 @@
 <?php
+{{#declareStrictTypes}}declare(strict_types=1);{{/declareStrictTypes}}
+
 /**
  * ApiException
  * PHP version 8.1
diff --git a/modules/openapi-generator/src/main/resources/php/Configuration.mustache b/modules/openapi-generator/src/main/resources/php/Configuration.mustache
index 5f8159b6a285..2caa16a8f54b 100644
--- a/modules/openapi-generator/src/main/resources/php/Configuration.mustache
+++ b/modules/openapi-generator/src/main/resources/php/Configuration.mustache
@@ -1,4 +1,5 @@
 <?php
+{{#declareStrictTypes}}declare(strict_types=1);{{/declareStrictTypes}}
 /**
  * Configuration
  * PHP version 8.1
diff --git a/modules/openapi-generator/src/main/resources/php/FormDataProcessor.mustache b/modules/openapi-generator/src/main/resources/php/FormDataProcessor.mustache
index 6985fd6c573f..7880339d7caa 100644
--- a/modules/openapi-generator/src/main/resources/php/FormDataProcessor.mustache
+++ b/modules/openapi-generator/src/main/resources/php/FormDataProcessor.mustache
@@ -1,4 +1,6 @@
 <?php
+{{#declareStrictTypes}}declare(strict_types=1);{{/declareStrictTypes}}
+
 /**
  * FormDataProcessor
  * PHP version 7.4
diff --git a/modules/openapi-generator/src/main/resources/php/HeaderSelector.mustache b/modules/openapi-generator/src/main/resources/php/HeaderSelector.mustache
index 1470695d3c23..9977e20be1e1 100644
--- a/modules/openapi-generator/src/main/resources/php/HeaderSelector.mustache
+++ b/modules/openapi-generator/src/main/resources/php/HeaderSelector.mustache
@@ -1,4 +1,5 @@
 <?php
+{{#declareStrictTypes}}declare(strict_types=1);{{/declareStrictTypes}}
 /**
  * HeaderSelector
  * PHP version 8.1
diff --git a/modules/openapi-generator/src/main/resources/php/ModelInterface.mustache b/modules/openapi-generator/src/main/resources/php/ModelInterface.mustache
index 4b0def70a90d..e8ca8126bc25 100644
--- a/modules/openapi-generator/src/main/resources/php/ModelInterface.mustache
+++ b/modules/openapi-generator/src/main/resources/php/ModelInterface.mustache
@@ -1,4 +1,5 @@
 <?php
+{{#declareStrictTypes}}declare(strict_types=1);{{/declareStrictTypes}}
 /**
  * ModelInterface
  *
diff --git a/modules/openapi-generator/src/main/resources/php/ObjectSerializer.mustache b/modules/openapi-generator/src/main/resources/php/ObjectSerializer.mustache
index 9bf66a48288f..eb5d0a2f0b3a 100644
--- a/modules/openapi-generator/src/main/resources/php/ObjectSerializer.mustache
+++ b/modules/openapi-generator/src/main/resources/php/ObjectSerializer.mustache
@@ -1,4 +1,5 @@
 <?php
+{{#declareStrictTypes}}declare(strict_types=1);{{/declareStrictTypes}}
 /**
  * ObjectSerializer
  *