php - 错误对象和数组

Question

我有这个代码

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

问题是有时我会收到此错误

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

第 988 行是我包含的上述行。我已经在检查它的对象或数组，那么为什么会出现这个错误？

Answer 1

它与优先级或 PHP 计算表达式的方式有关。用括号分组解决了这个问题:

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

请参阅此处的注释: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.
?>