PHP - extracting array values ( square brackets vs arrow notation )

Question

I have an object and when I user var_dump i get the following:

var_dump($object);

array (size=7)
  'id' => int 1969
  'alt' => string '' (length=0)
  'title' => string 'File Name' (length=9)
  'url' => string 'http://location/file.pdf' (length=24)

When I echo $object[url] it returns string 'http://location/file.pdf' (length=24), however when I echo $object->url I get null. (This sometimes works for extracting values from an array, I'm just not sure in which cases or what type of arrays)

The problem is that I use a hosting provider that has a git feature, and when I push my changes, it checks the PHP code and encounters a syntax error (unexpected '[') which halts the push.

My local server uses PHP 5.4.16 and the host uses 5.3.2

On a broader note, can someone point me to a resource that explains the difference between these two methods of extracting values from arrays? Much appreciated!

$var->foo is an object reference. $var[foo] is an array reference. While this sort of thign could be used interchangeably in some languages like javascript, in PHP an array and an object are two entirely different things. — Marc B
– Marc B, Commented Oct 3, 2014 at 14:52

Daan · Accepted Answer · 2014-10-03 14:51:22Z

13

You can't access arrays this way : -> that only applies to objects like the following:

$x = (object) array('a'=>'A', 'b'=>'B', 'C'); gives you:

stdClass Object
(
    [a] => A
    [b] => B
    [0] => C
)

To access these values you have to do it the way with -> like so:

$valA = $x->a;

answered Oct 3, 2014 at 14:51

Daan

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Mike Brant · Accepted Answer · 2017-03-03 20:13:49Z

11

You don't have an object, you have an associative array. Note the very first word in your var_dump() output is:

array

Thus $object->url has no meaning and should in fact give you an error about trying to access property of a non-object.

I could not imagine any PHP-related syntax checking process which would throw an error on something like $foo['bar']. Whether it is an object or array would typically not be able to be determined by a simple syntax check. You may have other typos somewhere preceding that are causing this though.

edited Mar 3, 2017 at 20:13

answered Oct 3, 2014 at 14:49

Mike Brant

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6 Comments

prodigitalson Over a year ago

To wit, -> is for accessing object with an object that implements ArrayAccess.

psorensen Over a year ago

Yes I am surprised by the error as well, but it only occurs when the bracket notation is present.

Mike Brant Over a year ago

@PeteSorensen Maybe a question for your hosting provider (or see if you can have them turn of syntax chaecking, as it would seem odd to run this as part of a push process.

psorensen Over a year ago

After using a syntax checker, it seems to be a problem with 5.3 and not 5.4. Still confused how to extract the single array value in 5.3

Mike Brant Over a year ago

@PeteSorensen In your case to get the url, you would need to do $object['url']. Of course $object is a really poor name for the variable in this case.

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