Resolving 'argument 1 Passed To Constructor Must Be An Instance Of Type, String Given' In Php

Resolving ‘Argument 1 Passed to Constructor Must Be an Instance of Type, String Given’ in PHP


When encountering the error message “Argument 1 passed to [class method] must be an instance of [type], string given” in PHP, it indicates that a method is expecting an object of a specific class as its first argument, but a string has been provided instead.




This error occurs when you attempt to pass a scalar value, such as a string, to a method that requires an object. This is a type mismatch issue, as PHP expects the first argument to be an object of a certain class.


class User {
    // constructor takes an object of type Address as its argument
    public function __construct(Address $address) {}

// trying to pass a string to the constructor
$user = new User('123 Main Street'); // results in the error message

// creating an Address object and passing it to the constructor
$address = new Address('123 Main Street');
$user = new User($address); // works correctly


To resolve this error, ensure that you are passing an object of the correct type to the method. In the example above, you should create an object of the Address class and pass it to the User constructor.

Additional Notes:

  • The specific type required by the method will vary depending on the class and its design.
  • You can check the method’s documentation or source code to determine the expected type of its arguments.
  • If you are certain that you are passing the correct type but still encounter this error, check for potential type casting or implicit conversions that may be causing the issue.## Resolving ‘argument 1 passed to Constructor must be an instance of Type, string given’ in PHP

Executive Summary

This comprehensive guide explores the ‘argument 1 passed to Constructor must be an instance of Type, string given’ error in PHP. By examining the error’s root causes, offering practical solutions, and delving into related concepts, this article equips developers with the necessary knowledge to effectively address and resolve this common programming issue.


The ‘argument 1 passed to Constructor must be an instance of Type, string given’ error in PHP occurs when an object is instantiated with an incorrect argument type. This error can disrupt development processes, affecting code execution and system stability. Understanding the underlying causes and resolving this error promptly is crucial to ensure seamless development and maintain code integrity.

Subtopic 1: Object-Oriented Programming (OOP)

OOP involves creating objects that interact and communicate through methods and properties. Each object belongs to a class, which defines its data structure and behavior. The error in question typically arises when attempting to instantiate an object without providing an appropriate class instance as an argument.

Subtopic 2: Class and Instance

A PHP class serves as a blueprint for creating objects with specific properties and methods. An instance of a class is a specific object created based on the class’s definition. To initialize an object properly, it’s essential to pass an instance of the correct class as an argument to the constructor.

Subtopic 3: Constructor

A constructor is a special method that initializes an object’s properties when the object is created. The constructor’s name matches the class name, and it must be public. The error ‘argument 1 passed to Constructor must be an instance of Type’ often indicates that the argument passed to the constructor was not a valid instance of the intended class.

Subtopic 4: Argument Type Checking

PHP utilizes static code analysis to ensure that arguments passed to functions and methods are of the appropriate type. This feature helps prevent various issues, including type inconsistencies that could lead to errors like the one in question.

Subtopic 5: Code Refactoring

In instances where code inherits from external classes or utilizes a third-party library, it may be necessary to refactor the code to ensure compatibility and prevent the ‘argument 1 passed to Constructor must be an instance of Type’ error. It is essential to adapt the code to match the expected class and argument types.


Addressing the ‘argument 1 passed to Constructor must be an instance of Type, string given’ error in PHP requires a multifaceted approach. By understanding OOP concepts, class and instance relationships, constructor functionality, argument type checking, and code refactoring, developers can effectively resolve this issue and ensure code quality and reliability.

Keyword Phrase Tags

  • PHP
  • Constructor
  • Object-Oriented Programming
  • Class Instance
  • Argument Type
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Comments 8
  1. Seems like a very interesting topic. I’m going to give it a try and see what I can come up with. Thanks for sharing!

  2. I’m not sure what you’re trying to say here. Can you please rewrite this in a more clear and concise way?

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