PHP恆裏面IF

Question

有問題在PHP想，如果有人可以解釋常數：

這個作品

const _ROOT = 'd:/aphp/www'; 

echo "r="._ROOT; 

爲做到這一點：

if (true) 
     define('_ROOT','d:/aphp/www'); 

echo "r="._ROOT; 

但是這給了錯誤：解析錯誤：語法錯誤，意外T_CONST

if (true) 
    const _ROOT = 'd:/aphp/www'; 

echo "r="._ROOT; 

我使用PHP 5.3.2

Answer 1

那是因爲...

的const關鍵字必須在頂層範圍

從PHP文件

Note: As opposed to defining constants using define(), constants defined using the const keyword must be declared at the top-level scope because they are defined at compile-time. This means that they cannot be declared inside functions, loops or if statements.

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