error object and array

Question

I have this code

$myvar = is_object($somevar) ? $somevar->value : is_array($somevar) ? $somevar['value'] : '';

issue is that sometime I am getting this error

PHP Error: Cannot use object of type \mypath\method as array in /var/www/htdocs/website/app/resources/tmp/cache/templates/template_view.html.php on line 988

line 988 is the above line I included. I am already checking if its object or array, so why this error then?

No Results Found · Accepted Answer · 2012-07-17 23:08:53Z

4

It has something to do with priority, or the way PHP is evaluating your expression. Grouping with parentheses solves the problem:

$myvar = is_object($somevar) ? $somevar->value : (is_array($somevar) ? $somevar['value'] : '');

See the notes here: http://www.php.net/manual/en/language.operators.comparison.php#language.operators.comparison.ternary

Note:

It is recommended that you avoid "stacking" ternary expressions. PHP's behaviour when using more than one ternary operator within a single statement is non-obvious:

Example #3 Non-obvious Ternary Behaviour

<?php
// on first glance, the following appears to output 'true'
echo (true?'true':false?'t':'f');

// however, the actual output of the above is 't'
// this is because ternary expressions are evaluated from left to right

// the following is a more obvious version of the same code as above
echo ((true ? 'true' : false) ? 't' : 'f');

// here, you can see that the first expression is evaluated to 'true', which
// in turn evaluates to (bool)true, thus returning the true branch of the
// second ternary expression.
?>

edited Jul 17, 2012 at 23:08

answered Jul 17, 2012 at 23:01

No Results Found

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6 Comments

Bailey Parker Over a year ago

I would +1 you for beating me to discovering the reason for need for the parens first, but I've reached my daily vote limit.

No Results Found Over a year ago

It's all good but thanks anyways. I really wish no one cared about who posted 10 seconds earlier and all that stuff, to me it's quality that should count. But anyways, I approve of your alternative (to me, readability tops brevity) so +1 for your contribution.

Bailey Parker Over a year ago

Agreed. But that's SO. The same rep system that was created to encourage quality posts also creates a competitive environment. And in this competition as in others, being first has some special value attached to it.

No Results Found Over a year ago

Being eager to answer first does have significant value to the OP of course (depending on the urgency of the problem), but it does get ridiculous when we're talking about seconds. But on topic: this is weird behavior on PHP's part and I had to test OP's code to believe it. I never nest conditional operators just because it looks confusing.

Bailey Parker Over a year ago

Should multiple answers be able to be marked as accepted then if they are of the same quality and both solve the problem at hand?

|

Bailey Parker · Accepted Answer · 2012-07-17 23:01:36Z

3

You need to place parenthesis around the second ternary:

$myvar = is_object($somevar) ? $somevar->value : (is_array($somevar) ? $somevar['value'] : '');

This must have something to do with operator precedence, though I'm not sure why yet.

Opinion: The ternary with or without parenthesis is difficult to read IMHO. I'd stick with the expanded form:

$myvar = '';

if(is_object($somevar)) {
    $myvar = $somevar->value;
} elseif(is_array($somevar)) {
    $myvar = $somevar['value'];
}

answered Jul 17, 2012 at 23:01

Bailey Parker

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Note:

Example #3 Non-obvious Ternary Behaviour

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