The ReflectionParameter class

(PHP 5, PHP 7)

Introduction

The ReflectionParameter class retrieves information about function's or method's parameters.

To introspect function parameters, first create an instance of the ReflectionFunction or ReflectionMethod classes and then use their ReflectionFunctionAbstract::getParameters() method to retrieve an array of parameters.

Class synopsis

ReflectionParameter implements Reflector {
/* Properties */
public $name ;
/* Methods */
public allowsNull ( void ) : bool
public canBePassedByValue ( void ) : bool
final private __clone ( void ) : void
public __construct ( string $function , string $parameter )
public static export ( string $function , string $parameter [, bool $return ] ) : string
public getClass ( void ) : ReflectionClass
public getDefaultValue ( void ) : mixed
public getDefaultValueConstantName ( void ) : string
public getName ( void ) : string
public getPosition ( void ) : int
public getType ( void ) : ReflectionType
public hasType ( void ) : bool
public isArray ( void ) : bool
public isCallable ( void ) : bool
public isDefaultValueAvailable ( void ) : bool
public isDefaultValueConstant ( void ) : bool
public isOptional ( void ) : bool
public isPassedByReference ( void ) : bool
public isVariadic ( void ) : bool
public __toString ( void ) : string
}

Properties

name

Name of the parameter. Read-only, throws ReflectionException in attempt to write.

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User Contributed Notes 3 notes

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9
fgm at riff dot org
10 years ago
The note about the signature of the ReflectionParameter constructor is actually incomplete, at least in 5.2.5: it is possible to use an integer for the second parameter, and the constructor will use it to return the n-th parameter.

This allows you to obtain proper ReflectionParameter objects even when documenting code from extensions which (strangely enough) define several parameters with the same name. The string-based constructor always returns the first parameter with the matching name, whereas the integer-based constructor correctly returns the n-th parameter.

So, in short, this works:
<?php
// supposing the extension defined something like:
// Some_Class::someMethod($a, $x, $y, $x, $y)
$p = new ReflectionParameter(array('Some_Class', 'someMethod'), 4);
// returns the last parameter, whereas
$p = new ReflectionParameter(array('Some_Class', 'someMethod'), 'y');
// always returns the first $y at position 2
?>
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2
killgecNOFSPAM at gmail dot com
11 years ago
Signature of constructor of ReflectionParameter correctly is:

public function __construct(array/string $function, string $name);

where $function is either a name of a global function, or a class/method name pair.
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1
massimo at mmware dot it
11 years ago
I found these limitations using class ReflectionParameter from ReflectionFunction with INTERNAL FUNCTIONS (eg print_r, str_replace, ... ) :

1. parameter names don't match with manual: (try example 19.35 with arg "call_user_func" )
2. some functions (eg PCRE function, preg_match etc) have EMPTY parameter names
3. calling getDefaultValue on Parameters will result in Exception "Cannot determine default value for internal functions"
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