php isset() on a string variable using a string as index

Question

I have some strange issue with isset() function in PHP. Let me show... .

<?php

$aTestArray = array(
    'index' => array(
        'index' => 'Główna'
    ),
    'dodaj' => 'Dodaj ogłoszenie',
);

var_dump( isset($aTestArray['index']) );
var_dump( isset($aTestArray['index']['index']) );
var_dump( isset($aTestArray['dodaj']) );

var_dump( isset($aTestArray['index']['none']) );
var_dump( isset($aTestArray['index']['none']['none2']) );

// This unexpectedly returns TRUE
var_dump( isset($aTestArray['dodaj']['none']) );
var_dump( isset($aTestArray['dodaj']['none']['none2']) );


?>

The var_dump's will return:

bool(true)
bool(true)
bool(true)

bool(false)
bool(false)
bool(true)
bool(false)

Why the sixth var_dump() return TRUE ?

Tom van der Woerdt · Accepted Answer · 2011-12-03 23:15:01Z

12

When using the [] operators on a string, it will expect an integer value. If it does not get one, it will convert it. ['none'] is converted to [0] which, in your case, is a D.

answered Dec 3, 2011 at 23:15

Tom van der Woerdt

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8 Comments

Bojangles Over a year ago

Incorrect. One of the best features of PHP is that it does allow string keys; ['none'] is a valid key name.

Michael Berkowski Over a year ago

+1 Also good to explain that using [] on a string attempts to access its characters as array components.

Tom van der Woerdt Over a year ago

@JamWaffles Absolutely! But that's when working with associative arrays. In this case we're doing something like 'Dodaj ogłoszenie'['none'], which does not support named keys.

Bojangles Over a year ago

@TomvanderWoerdt Ah I see now. I should have read the question more carefully - sorry!

NikiC Over a year ago

This by the way may change in PHP 5.4. This "feature" has been found problematic when seen together with string offset reading related changes in 5.4. It is currently being discussed to throw a notice in this case.

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Sergej Brazdeikis · Accepted Answer · 2011-12-03 23:25:21Z

1

It is because PHP is written in C. So since $aTestArray['dodaj'] is the string:

$aTestArray['dodaj']['none']

is the same as

$aTestArray['dodaj'][0]

because

var_dump( (int) 'none')

is 0

answered Dec 3, 2011 at 23:25

Sergej Brazdeikis

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1 Comment

The Nail Over a year ago

This answer would be much more useful if it were changed into an explanatory comment to Tom's answer.

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