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Type hinting generic objects

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Since PHP objects don’t inherit from any base class (including stdClass), there is no support for type hinting a generic object type.

For example, the below will not work. 

<?php

function doSomething(object $obj) {
    return $obj;
}

class ClassOne {}
class ClassTwo {}

$classOne= new ClassOne();
$classTwo= new ClassTwo();

doSomething($classOne);
doSomething($classTwo);

And will throw a fatal error:

Fatal error: Uncaught TypeError: Argument 1 passed to doSomething() must be an instance of object, instance of OperationOne given

A workaround to this is to declare a degenerate interface that defines no methods, and have all of your objects implement this interface. 

<?php

interface Object {}

function doSomething(Object $obj) {
    return $obj;
}

class ClassOne implements Object {}
class ClassTwo implements Object {}

$classOne = new ClassOne();
$classTwo = new ClassTwo();

doSomething($classOne);
doSomething($classTwo);
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Type hinting:
* Type hinting
* Type hinting classes and interfaces
* Type hinting scalar types arrays and callables
* Nullable type hints
* Type hinting generic objects
* Type Hinting No ReturnVoid
Table Of Contents
0 Getting started
1 Variables
2 Arrays
3 Functional programming
4 Types
5 Autoloading primer
6 Exception handling and error reporting
7 Working with dates and time
8 Sending email
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24 Composer dependency manager
25 Magic methods
26 Alternative syntax for control structures
27 File handling
28 Magic constants
29 Type hinting
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31 Filters, filter functions
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35 UTF-8
36 URLs
37 Object serialization
38 PHPDoc
39 Contributing to PHP Manual
40 String parsing
41 Loops
42 Control structures
43 Serialization
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46 Type juggling and non-strict comparison issues
47 Security
48 PHP MySQLi
49 Command Line Interface CLI
50 Localization
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52 Superglobal variables
53 Unit testing
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55 References
56 Compilation errors and warning
57 Installing PHP on Windows
58 DateTime class
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60 Performance
61 Common Errors
62 Installing on Linux / Unix
63 Contributing to PHP Core
64 Coding conventions
65 Using MongoDB
66 Asynchronous programming
67 Using SQLSRV
68 Unicode Support
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71 Hot to detect client IP address
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84 Outputting the value of a variable
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87 MongoDB
88 Manipulating an array
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90 Processing multiple arrays together
91 SPL data structures
92 Comments
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97 HTTP Authentication
98 Recipies
99 BC Math Binary Calculator
100 Docker deployment
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102 APCu
103 Design patterns
104 Secure remember me
105 PHP mysqli
106 PHP built-in server
107 How to break down an URL
108 PSR
109 Contributors