# Error levels You can run Psalm in at different levels of strictness from 1 to 8. Level 1 is the most strict, level 8 is the most lenient. When no level is explicitly defined, psalm defaults to level 2. Some issues are always treated as errors. These are issues with a very low probability of false-positives. At level 1 all issues (except those emitted for opt-in features) that Psalm can find are treated as errors. Those issues include any situation where Psalm cannot infer the type of a given expression. At level 2 Psalm ignores those `Mixed*` issues, but treats most other issues as errors. At level 3 Psalm starts to be a little more lenient. For example Psalm allows missing param types, return types and property types. At level 4 Psalm ignores issues for _possible_ problems. These are more likely to be false positives – where the application code may guarantee behaviour that Psalm isn't able to infer. Level 5 and above allows a more non-verifiable code, and higher levels are even more permissive. ## Always treated as errors - [AbstractMethodCall](issues/AbstractMethodCall.md) - [ComplexFunction](issues/ComplexFunction.md) - [ComplexMethod](issues/ComplexMethod.md) - [ConfigIssue](issues/ConfigIssue.md) - [DuplicateArrayKey](issues/DuplicateArrayKey.md) - [DuplicateClass](issues/DuplicateClass.md) - [DuplicateFunction](issues/DuplicateFunction.md) - [DuplicateMethod](issues/DuplicateMethod.md) - [DuplicateParam](issues/DuplicateParam.md) - [EmptyArrayAccess](issues/EmptyArrayAccess.md) - [ExtensionRequirementViolation](issues/ExtensionRequirementViolation.md) - [ImplementationRequirementViolation](issues/ImplementationRequirementViolation.md) - [ImpureByReferenceAssignment](issues/ImpureByReferenceAssignment.md) - [ImpureFunctionCall](issues/ImpureFunctionCall.md) - [ImpureMethodCall](issues/ImpureMethodCall.md) - [ImpurePropertyAssignment](issues/ImpurePropertyAssignment.md) - [ImpurePropertyFetch](issues/ImpurePropertyFetch.md) - [ImpureStaticProperty](issues/ImpureStaticProperty.md) - [ImpureStaticVariable](issues/ImpureStaticVariable.md) - [ImpureVariable](issues/ImpureVariable.md) - [InaccessibleClassConstant](issues/InaccessibleClassConstant.md) - [InaccessibleMethod](issues/InaccessibleMethod.md) - [InaccessibleProperty](issues/InaccessibleProperty.md) - [InterfaceInstantiation](issues/InterfaceInstantiation.md) - [InvalidAttribute](issues/InvalidAttribute.md) - [InvalidEnumMethod](issues/InvalidEnumMethod.md) - [InvalidExtendClass](issues/InvalidExtendClass.md) - [InvalidGlobal](issues/InvalidGlobal.md) - [InvalidParamDefault](issues/InvalidParamDefault.md) - [InvalidParent](issues/InvalidParent.md) - [InvalidPassByReference](issues/InvalidPassByReference.md) - [InvalidScope](issues/InvalidScope.md) - [InvalidStaticInvocation](issues/InvalidStaticInvocation.md) - [InvalidThrow](issues/InvalidThrow.md) - [LoopInvalidation](issues/LoopInvalidation.md) - [MethodSignatureMustOmitReturnType](issues/MethodSignatureMustOmitReturnType.md) - [MethodSignatureMustProvideReturnType](issues/MethodSignatureMustProvideReturnType.md) - [MissingDependency](issues/MissingDependency.md) - [MissingFile](issues/MissingFile.md) - [MissingImmutableAnnotation](issues/MissingImmutableAnnotation.md) - [MissingTemplateParam](issues/MissingTemplateParam.md) - [MissingThrowsDocblock](issues/MissingThrowsDocblock.md) - [NonStaticSelfCall](issues/NonStaticSelfCall.md) - [NoValue](issues/NoValue.md) - [NullArrayAccess](issues/NullArrayAccess.md) - [NullFunctionCall](issues/NullFunctionCall.md) - [NullIterator](issues/NullIterator.md) - [NullPropertyAssignment](issues/NullPropertyAssignment.md) - [NullPropertyFetch](issues/NullPropertyFetch.md) - [NullReference](issues/NullReference.md) - [OverriddenPropertyAccess](issues/OverriddenPropertyAccess.md) - [ParadoxicalCondition](issues/ParadoxicalCondition.md) - [ParentNotFound](issues/ParentNotFound.md) - [TooFewArguments](issues/TooFewArguments.md) - [UndefinedAttributeClass](issues/UndefinedAttributeClass.md) - [UndefinedClass](issues/UndefinedClass.md) - [UndefinedConstant](issues/UndefinedConstant.md) - [UndefinedDocblockClass](issues/UndefinedDocblockClass.md) - [UndefinedFunction](issues/UndefinedFunction.md) - [UndefinedGlobalVariable](issues/UndefinedGlobalVariable.md) - [UndefinedInterface](issues/UndefinedInterface.md) - [UndefinedTrait](issues/UndefinedTrait.md) - [UndefinedVariable](issues/UndefinedVariable.md) - [UnimplementedAbstractMethod](issues/UnimplementedAbstractMethod.md) - [UnimplementedInterfaceMethod](issues/UnimplementedInterfaceMethod.md) - [UnrecognizedExpression](issues/UnrecognizedExpression.md) - [UnrecognizedStatement](issues/UnrecognizedStatement.md) - [UnusedFunctionCall](issues/UnusedFunctionCall.md) - [UnusedMethodCall](issues/UnusedMethodCall.md) ## Errors that appear at level 7 and below - [AbstractInstantiation](issues/AbstractInstantiation.md) - [AssignmentToVoid](issues/AssignmentToVoid.md) - [CircularReference](issues/CircularReference.md) - [ConflictingReferenceConstraint](issues/ConflictingReferenceConstraint.md) - [ContinueOutsideLoop](issues/ContinueOutsideLoop.md) - [InvalidTypeImport](issues/InvalidTypeImport.md) - [MethodSignatureMismatch](issues/MethodSignatureMismatch.md) - [OverriddenMethodAccess](issues/OverriddenMethodAccess.md) - [ParamNameMismatch](issues/ParamNameMismatch.md) - [ReservedWord](issues/ReservedWord.md) - [UnhandledMatchCondition](issues/UnhandledMatchCondition.md) - [UninitializedProperty](issues/UninitializedProperty.md) ## Errors that appear at level 6 and below - [InvalidArgument](issues/InvalidArgument.md) - [InvalidArrayAccess](issues/InvalidArrayAccess.md) - [InvalidArrayAssignment](issues/InvalidArrayAssignment.md) - [InvalidArrayOffset](issues/InvalidArrayOffset.md) - [InvalidCast](issues/InvalidCast.md) - [InvalidCatch](issues/InvalidCatch.md) - [InvalidClass](issues/InvalidClass.md) - [InvalidClone](issues/InvalidClone.md) - [InvalidFunctionCall](issues/InvalidFunctionCall.md) - [InvalidIterator](issues/InvalidIterator.md) - [InvalidMethodCall](issues/InvalidMethodCall.md) - [InvalidNamedArgument](issues/InvalidNamedArgument.md) - [InvalidPropertyAssignment](issues/InvalidPropertyAssignment.md) - [InvalidPropertyAssignmentValue](issues/InvalidPropertyAssignmentValue.md) - [InvalidPropertyFetch](issues/InvalidPropertyFetch.md) - [InvalidReturnStatement](issues/InvalidReturnStatement.md) - [InvalidReturnType](issues/InvalidReturnType.md) - [InvalidTemplateParam](issues/InvalidTemplateParam.md) - [NullArgument](issues/NullArgument.md) - [NullArrayOffset](issues/NullArrayOffset.md) - [TooManyTemplateParams](issues/TooManyTemplateParams.md) - [TraitMethodSignatureMismatch](issues/TraitMethodSignatureMismatch.md) - [UndefinedMethod](issues/UndefinedMethod.md) - [UndefinedPropertyAssignment](issues/UndefinedPropertyAssignment.md) - [UndefinedPropertyFetch](issues/UndefinedPropertyFetch.md) - [UndefinedThisPropertyFetch](issues/UndefinedThisPropertyFetch.md) ## Errors that appear at level 5 and below - [ConstructorSignatureMismatch](issues/ConstructorSignatureMismatch.md) - [FalsableReturnStatement](issues/FalsableReturnStatement.md) - [InvalidNullableReturnType](issues/InvalidNullableReturnType.md) - [LessSpecificImplementedReturnType](issues/LessSpecificImplementedReturnType.md) - [MoreSpecificImplementedParamType](issues/MoreSpecificImplementedParamType.md) - [NullableReturnStatement](issues/NullableReturnStatement.md) - [UndefinedInterfaceMethod](issues/UndefinedInterfaceMethod.md) - [UndefinedThisPropertyAssignment](issues/UndefinedThisPropertyAssignment.md) ## Errors that appear at level 4 and below - [FalseOperand](issues/FalseOperand.md) - [ForbiddenCode](issues/ForbiddenCode.md) - [ImplementedParamTypeMismatch](issues/ImplementedParamTypeMismatch.md) - [ImplementedReturnTypeMismatch](issues/ImplementedReturnTypeMismatch.md) - [ImplicitToStringCast](issues/ImplicitToStringCast.md) - [InternalClass](issues/InternalClass.md) - [InternalMethod](issues/InternalMethod.md) - [InternalProperty](issues/InternalProperty.md) - [InvalidDocblock](issues/InvalidDocblock.md) - [InvalidLiteralArgument](issues/InvalidLiteralArgument.md) - [InvalidOperand](issues/InvalidOperand.md) - [InvalidScalarArgument](issues/InvalidScalarArgument.md) - [InvalidToString](issues/InvalidToString.md) - [MismatchingDocblockParamType](issues/MismatchingDocblockParamType.md) - [MismatchingDocblockReturnType](issues/MismatchingDocblockReturnType.md) - [MissingDocblockType](issues/MissingDocblockType.md) - [NoInterfaceProperties](issues/NoInterfaceProperties.md) - [PossibleRawObjectIteration](issues/PossibleRawObjectIteration.md) - [RedundantCondition](issues/RedundantCondition.md) - [RedundantFunctionCall](issues/RedundantFunctionCall.md) - [RedundantPropertyInitializationCheck](issues/RedundantPropertyInitializationCheck.md) - [StringIncrement](issues/StringIncrement.md) - [TooManyArguments](issues/TooManyArguments.md) - [TypeDoesNotContainNull](issues/TypeDoesNotContainNull.md) - [TypeDoesNotContainType](issues/TypeDoesNotContainType.md) - [UndefinedMagicMethod](issues/UndefinedMagicMethod.md) - [UndefinedMagicPropertyAssignment](issues/UndefinedMagicPropertyAssignment.md) - [UndefinedMagicPropertyFetch](issues/UndefinedMagicPropertyFetch.md) ## Errors that appear at level 3 and below - [ArgumentTypeCoercion](issues/ArgumentTypeCoercion.md) - [LessSpecificReturnStatement](issues/LessSpecificReturnStatement.md) - [MoreSpecificReturnType](issues/MoreSpecificReturnType.md) - [PossiblyFalseArgument](issues/PossiblyFalseArgument.md) - [PossiblyFalseIterator](issues/PossiblyFalseIterator.md) - [PossiblyFalseOperand](issues/PossiblyFalseOperand.md) - [PossiblyFalsePropertyAssignmentValue](issues/PossiblyFalsePropertyAssignmentValue.md) - [PossiblyFalseReference](issues/PossiblyFalseReference.md) - [PossiblyInvalidArgument](issues/PossiblyInvalidArgument.md) - [PossiblyInvalidArrayAccess](issues/PossiblyInvalidArrayAccess.md) - [PossiblyInvalidArrayAssignment](issues/PossiblyInvalidArrayAssignment.md) - [PossiblyInvalidArrayOffset](issues/PossiblyInvalidArrayOffset.md) - [PossiblyInvalidCast](issues/PossiblyInvalidCast.md) - [PossiblyInvalidClone](issues/PossiblyInvalidClone.md) - [PossiblyInvalidFunctionCall](issues/PossiblyInvalidFunctionCall.md) - [PossiblyInvalidIterator](issues/PossiblyInvalidIterator.md) - [PossiblyInvalidMethodCall](issues/PossiblyInvalidMethodCall.md) - [PossiblyInvalidOperand](issues/PossiblyInvalidOperand.md) - [PossiblyInvalidPropertyAssignment](issues/PossiblyInvalidPropertyAssignment.md) - [PossiblyInvalidPropertyAssignmentValue](issues/PossiblyInvalidPropertyAssignmentValue.md) - [PossiblyInvalidPropertyFetch](issues/PossiblyInvalidPropertyFetch.md) - [PossiblyNullArgument](issues/PossiblyNullArgument.md) - [PossiblyNullArrayAccess](issues/PossiblyNullArrayAccess.md) - [PossiblyNullArrayAssignment](issues/PossiblyNullArrayAssignment.md) - [PossiblyNullArrayOffset](issues/PossiblyNullArrayOffset.md) - [PossiblyNullFunctionCall](issues/PossiblyNullFunctionCall.md) - [PossiblyNullIterator](issues/PossiblyNullIterator.md) - [PossiblyNullPropertyAssignment](issues/PossiblyNullPropertyAssignment.md) - [PossiblyNullPropertyAssignmentValue](issues/PossiblyNullPropertyAssignmentValue.md) - [PossiblyNullPropertyFetch](issues/PossiblyNullPropertyFetch.md) - [PossiblyNullReference](issues/PossiblyNullReference.md) - [PossiblyUndefinedArrayOffset](issues/PossiblyUndefinedArrayOffset.md) - [PossiblyUndefinedGlobalVariable](issues/PossiblyUndefinedGlobalVariable.md) - [PossiblyUndefinedMethod](issues/PossiblyUndefinedMethod.md) - [PossiblyUndefinedVariable](issues/PossiblyUndefinedVariable.md) - [PropertyTypeCoercion](issues/PropertyTypeCoercion.md) - [RiskyCast](issues/RiskyCast.md) ## Errors that appear at level 2 and below - [DeprecatedClass](issues/DeprecatedClass.md) - [DeprecatedConstant](issues/DeprecatedConstant.md) - [DeprecatedFunction](issues/DeprecatedFunction.md) - [DeprecatedInterface](issues/DeprecatedInterface.md) - [DeprecatedMethod](issues/DeprecatedMethod.md) - [DeprecatedProperty](issues/DeprecatedProperty.md) - [DeprecatedTrait](issues/DeprecatedTrait.md) - [DocblockTypeContradiction](issues/DocblockTypeContradiction.md) - [InvalidDocblockParamName](issues/InvalidDocblockParamName.md) - [InvalidFalsableReturnType](issues/InvalidFalsableReturnType.md) - [InvalidStringClass](issues/InvalidStringClass.md) - [MissingClosureParamType](issues/MissingClosureParamType.md) - [MissingClosureReturnType](issues/MissingClosureReturnType.md) - [MissingConstructor](issues/MissingConstructor.md) - [MissingParamType](issues/MissingParamType.md) - [MissingPropertyType](issues/MissingPropertyType.md) - [MissingReturnType](issues/MissingReturnType.md) - [NullOperand](issues/NullOperand.md) - [PropertyNotSetInConstructor](issues/PropertyNotSetInConstructor.md) - [RawObjectIteration](issues/RawObjectIteration.md) - [RedundantConditionGivenDocblockType](issues/RedundantConditionGivenDocblockType.md) - [RedundantFunctionCallGivenDocblockType](issues/RedundantFunctionCallGivenDocblockType.md) - [ReferenceConstraintViolation](issues/ReferenceConstraintViolation.md) - [UndefinedTrace](issues/UndefinedTrace.md) - [UnresolvableInclude](issues/UnresolvableInclude.md) - [UnsafeInstantiation](issues/UnsafeInstantiation.md) ## Errors that only appear at level 1 - [LessSpecificReturnType](issues/LessSpecificReturnType.md) - [MixedArgument](issues/MixedArgument.md) - [MixedArgumentTypeCoercion](issues/MixedArgumentTypeCoercion.md) - [MixedArrayAccess](issues/MixedArrayAccess.md) - [MixedArrayAssignment](issues/MixedArrayAssignment.md) - [MixedArrayOffset](issues/MixedArrayOffset.md) - [MixedArrayTypeCoercion](issues/MixedArrayTypeCoercion.md) - [MixedAssignment](issues/MixedAssignment.md) - [MixedClone](issues/MixedClone.md) - [MixedFunctionCall](issues/MixedFunctionCall.md) - [MixedInferredReturnType](issues/MixedInferredReturnType.md) - [MixedMethodCall](issues/MixedMethodCall.md) - [MixedOperand](issues/MixedOperand.md) - [MixedPropertyAssignment](issues/MixedPropertyAssignment.md) - [MixedPropertyFetch](issues/MixedPropertyFetch.md) - [MixedPropertyTypeCoercion](issues/MixedPropertyTypeCoercion.md) - [MixedReturnStatement](issues/MixedReturnStatement.md) - [MixedReturnTypeCoercion](issues/MixedReturnTypeCoercion.md) - [MixedStringOffsetAssignment](issues/MixedStringOffsetAssignment.md) - [MutableDependency](issues/MutableDependency.md) - [PossiblyNullOperand](issues/PossiblyNullOperand.md) - [RedundantIdentityWithTrue](issues/RedundantIdentityWithTrue.md) - [Trace](issues/Trace.md) ## Feature-specific errors - [PossiblyUndefinedIntArrayOffset](issues/PossiblyUndefinedIntArrayOffset.md) - [PossiblyUndefinedStringArrayOffset](issues/PossiblyUndefinedStringArrayOffset.md) - [PossiblyUnusedMethod](issues/PossiblyUnusedMethod.md) - [PossiblyUnusedParam](issues/PossiblyUnusedParam.md) - [PossiblyUnusedProperty](issues/PossiblyUnusedProperty.md) - [TaintedCallable](issues/TaintedCallable.md) - [TaintedCookie](issues/TaintedCookie.md) - [TaintedCustom](issues/TaintedCustom.md) - [TaintedEval](issues/TaintedEval.md) - [TaintedFile](issues/TaintedFile.md) - [TaintedHeader](issues/TaintedHeader.md) - [TaintedHtml](issues/TaintedHtml.md) - [TaintedInclude](issues/TaintedInclude.md) - [TaintedInput](issues/TaintedInput.md) - [TaintedLdap](issues/TaintedLdap.md) - [TaintedShell](issues/TaintedShell.md) - [TaintedSql](issues/TaintedSql.md) - [TaintedSSRF](issues/TaintedSSRF.md) - [TaintedSystemSecret](issues/TaintedSystemSecret.md) - [TaintedUnserialize](issues/TaintedUnserialize.md) - [TaintedUserSecret](issues/TaintedUserSecret.md) - [UncaughtThrowInGlobalScope](issues/UncaughtThrowInGlobalScope.md) - [UnevaluatedCode](issues/UnevaluatedCode.md) - [UnnecessaryVarAnnotation](issues/UnnecessaryVarAnnotation.md) - [UnusedClass](issues/UnusedClass.md) - [UnusedClosureParam](issues/UnusedClosureParam.md) - [UnusedConstructor](issues/UnusedConstructor.md) - [UnusedForeachValue](issues/UnusedForeachValue.md) - [UnusedMethod](issues/UnusedMethod.md) - [UnusedParam](issues/UnusedParam.md) - [UnusedProperty](issues/UnusedProperty.md) - [UnusedPsalmSuppress](issues/UnusedPsalmSuppress.md) - [UnusedVariable](issues/UnusedVariable.md)