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PHP tips and tricks
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PHP tips and tricks

Contents:

  • Introduction
  • PHP tips and tricks
    • Duplicate Type
    • Yield Or Return
    • Multiple Method In Interface
    • Operator Overloading
    • Three Return Errors
    • array_unique() Is Slow
    • Cloning Static Variable
    • Datetime And Leap Second
    • Silent Type Cast
    • Objects As Keys In Foreach
    • isset() On Uninitialized Properties
    • Recycle Generator
    • Of Integers And Floats
    • max() On Strings
    • e And Euler
    • Closure On Constructor
    • ++ Riddle
    • Oversigned Integers
    • Local Variable Cost
    • Array Items By Value
    • Not Set But Exists
    • Sorting Enum
    • Hypotenuse In Action
    • Spaceship Always False
    • Inverted Spaceship Results
    • isset(), empty() And the Magic Methods
    • Comparing Arrays And Object
    • Mixed Compatibility
    • Where Did The Comma Go?
    • Argument Renaming
    • When htmlemtities() Is Failing
    • Static Arrow Function
    • defined() In Action
    • expm1() And log1p()
    • Is A Class Constant Set?
    • preg_split() Magic
    • Comparing NAN
    • array_unique() And Enum
    • Display A Tree Natively
    • Speed Up CSV Write To Disk
    • php://memory And Maxmemory
    • ::parent Operator
    • Stuttering PHP
    • Riddle: $this<-code
    • Multiple Const Types
    • Replacing PHP http Wrapper
    • Cast But Not A Cast
    • Hexadecimal Separator
    • Call echo With Commas
    • Reusing Decimals For Bananas
    • Where To Put The Cast?
    • Unpacking A Single Element Array
    • Abstract Or Not
    • (int) And (ant)
    • Cast In Const
    • global Overwrites
    • Property Hooks And Default Values
    • Static And Not Static Method
    • intval() And Its Arguments
    • Easy Map
    • Returning Void
    • Casting An Enum Case
    • Dynamic Class Constant Edge Cases
    • Dynamic Enum Cases
    • Yield And Keys
    • Array Callback Index
    • Time Of Closure Creation
    • Coalesce And The Fatal Error
    • Weakmap And Enums
    • parent In Function
    • isset() And The Fatal Error
    • All PHP Dereferencements
    • No Property Beyond Limits
    • Can’t Be Compatible With Less Arguments
    • Arrow Functions Import Variables By Values
    • Never Is The Lowest Ranking Type
    • The Never Function Arrow
    • No Rewrite For Exit
    • Alias Conflicts
    • Not All Incremented Strings Are Deprecated
    • get_class() Or ::class?
    • No Binding But With Original
    • Infinite foreach()
    • Who Modifies This Property?
    • mixed Is Not No Type
    • The Recursive array_merge()
    • $GLOBALS Is Not Defined
    • Cast Private To Array
    • Properties In Interfaces
    • Bitwise Operations On String
    • Typed Variables
    • Type And Reference
    • Chaining Spaceship
    • parse_str() Edge Cases
    • Cast A Closure To Array
    • list() Does Not Type
    • Triple Plus Operator
    • Function Name In A Method
    • PHP Quine
    • Named Parameter In An Array
    • self Is A Valid Type On A Closure
    • Keep Interface New Argument Compatible
    • Undefined Constant A On Its Line Of Definition
    • http_build_query() And Enumerations
    • Cannot indirectly modify readonly
    • Ellipsis And Coalesce
    • namespace namespace
    • Namespace, But Far In The Name
    • No Hidden Nullable
    • Remove Last Item In An Array
    • Cancelling Native Function
    • Classes Constant Disambiguation With Parenthesis
    • compact() Is Recursive
    • No Final Parameter
    • Is Not A NAN
    • Impossible Named Arguments
    • func_get_args() Skips Variadic
    • Ellipsis With Array Parameters
    • Named Parameter Inheritance
    • __invoke() On New
    • Method Or Property?
    • No More Class _
    • Method Not Property Name Must Be String
    • Static Properties
    • The New And The Parenthesis
    • Fluent Function
    • Cannot Use Isset On Expression, So Use What?
    • Constant Redefinition
    • No Class Constant In String
    • Return Int Not Bool
    • By Reference, Error Or Notice?
    • Call Function With Strings
    • Non Empty Match
    • Named Sqlite3 In Memory
    • Variable Creation
    • All Enum Cases
    • Unicode Comments
    • Datetime Object, And Years
    • Escaping A Regex
    • Every Anonymous Class Is Different
    • instanceof With Variables
    • Undefined Variable
    • Compatible Signature
    • private Is Relaxed
    • Class Implement No More
    • Variadic Are Typed And Defaulted
    • array_column() To Hash
    • \array Was Customizable
    • array Is Not An Array
    • array_map_assoc() With Keys
    • array_map() Goes Full Throttle
    • Typed Array
    • Initialize Readonly On Child
    • Silent Optimisation Of Variables
    • Modify String With Array Syntax
    • No Force Object To String
    • __invoke() Method And Properties
    • Constructor Needed
    • No Self Referencing Constants
    • Deanonymize Class
    • Noscream On Ellipsis
    • Incompatible Promoted Readonly
    • Where Is The Semicolon?
    • Self As Attribute
    • Reading Micro-seconds
    • Promoted Properties Compatibility
    • Enum Are Not Linted
    • Sorting With Minus
    • Override With Interface
    • Send An Argument To Generator
    • PHP Integer Format
    • Compatible Only Interface
    • No Cast In Constant Expressions
    • Lots Of Silly Arguments
    • Child Of Attribute Is Not An Attribute
    • Dynamic Class Constant
    • The Function Method
    • Match() With Multiple Values
    • Interfaces Constants Conflicts
    • Foreach() Skips Uninitialized Properties
    • Casting And Power
    • Attribute Without Class
    • Class Is A Valid Type
    • Float Precision
    • Store Float As Index
    • Case Insensitive Cast
    • $this $this
    • No Returntype But Still, Only String
    • No Unknown For array_merge()
    • No Returntype Enforced
    • As As As
    • No DNF For Catch
    • new On Object
    • Unfinished Class Doesn’t Compile
    • Yield, Not Return By Reference
    • class_exists() With Enums
    • No Semicolon In Sight
    • glob() With Hidden Files
    • A Function Called file_append_contents()
    • array_reduce() To Filter And Alter
    • $this Is Not Of The Current Class
    • Class Constants With Different Types
    • No Change To $this
    • file_put_contents() With Array Argument
    • Get The Generator
    • Redefine Native Functions
    • A Static Method Cannot Call A Non Static Method
    • Declared Before Or After
    • Cast Is So Strong
    • Roman Loops
    • Finally Catches Exception
    • Abstract Again
    • Always Compatible Variadic
    • Yield, Not Return
    • try, catch, finally Are All Optional
    • null Or Boolean As Array
    • Hide Sensitive Parameter
    • No Property In Interface
    • The Uncallable Function
    • Easy Wither Call
    • Array Is Full
    • Const Without Parenthesis
    • Cast Are Case Insensitive
    • Array And Object Syntax, Not The Same Error
    • When Space Matters
    • array array = array()
    • Cannot Yield And Never
    • Class Invasion Both Ways
    • Typed By Enum
    • Change A Static Variable Outside Its Function
    • Scalar Types Are Unqualified
    • array_append() And Short Assignation
    • Coalesce And Null
    • All Classes Aliases
    • Mixed And Untyped Are Not Compatible Types
    • Abstract Constants
    • Cannot Static Static Property
    • More Attribute Usage
    • Run Any Script In A Phar
    • Static Variable Outside A Method
    • Enumeration’s Cases Comparisons
    • All Static Curly Syntaxes And One Wrong
    • No Such Function As Empty
    • Strange –> Operator
    • Unexpected Keys In Array
    • Recursive Generator
    • Documenting Parameters
    • Catch Is Optional
    • Void Parameter In array_keys()
    • Unsetting Properties Surprises
    • Multiple Aliases
    • Plus Plus Minus Minus
    • Constants Can Be Impossible
    • Constants Are Mutable
    • Quick DTO Or VO Copy
    • Stealth Generator
    • Quick Serialize
    • Clone Clone Clone
    • Set readonly Properties Outside The Class
    • Exception Polymorphism
    • Exponential Minus One
    • PHP Infinity Is Reachable
    • Negative Squares
    • Negating An Assignation
    • Numeric Separators Inside A String?
    • Identifier Confusions
    • Relaxed Syntax With Const
    • Closure To Call
    • Get $this In A Static
    • How To array_intersect_uassoc_insensitive()
    • Class And Constant Confusion
    • Don’t Forget To Yield
    • Inconsistent Constructor Signatures
    • foreach() With All The Same Keys
    • Battle Of Definition
    • Variadic All The Yields
    • Refactoring strpos()
    • is_a() Versus Instanceof
    • Exporting Properties
    • Another Cast To Int
    • ReturnTypeWillChange Is For All
    • URL As Comments
    • Coalesce And Assignation
    • Missing Methods Are Fatal
    • Only Initialize With Short Assignation Coalesce
    • Keys Are Integers Whenever Possible
    • Fast Creation Of stdClass Objects
    • An Elephpant In The Code
    • Internal Static Call
    • strict_types Exceptions
    • Playing With Integers Limits
    • Signature Compatibility Exception
    • Object Is Not A Type
    • Forgotten Throw
    • Keywords In Namespaces
    • No Warning For Unused Variables
    • Self In An Interface
    • instanceof Object
    • stdClass Object
    • A Case Of Misplaced Parenthesis
    • Checking For Names At Different Times
    • Integer Becomes Negative
    • Not All Strings In Arrays
    • Recursive Arrow Function
    • null Does Not Always Equal false
    • Recursive Closure
    • Cast Precedence
    • Enum As A Name
    • Type Is Not Always Returned
    • The Namespace Stack
    • Catch On Interfaces
  • Author index
  • Error Message index
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Promoted Properties Compatibility¶

../_images/promoted_compatibility.png

Promoted properties are defined in a constructor signature. They cannot be defined in an abstract method, so they are not allowed in an abstract constructor: this is true in an abstract class and in an interface.

On the other hand, it is allowed to extend promoted properties without the promotion, and vice versa.

See Also¶

  • Class Abstract (PHP manual)

  • Promoting and compatibility [Try me]

PHP Features¶

  • abstract

  • property

  • constructor

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    • See Also
    • PHP Features