未加载包含文件的某些内容

Question

我正在尝试使用include_once（）php api将文件（myfile.php）的内容加载到另一个（index.php）中。但它没有加载内容。

// contents inside index page
if(include_once('myfile.php')){
    echo D; // this is working
    echo $b; // this is not working
} else {
    echo "unable to include the file";
}   

// contents inside myfile.php
define('D', '123');
$b = "abcd";

Answer 1

您可能没有正确包含它。

您可以找到in the documentation：

<?php
// won't work, evaluated as include(('vars.php') == 'OK'), i.e. include('')
if (include('vars.php') == 'OK') {
    echo 'OK';
}

// works
if ((include 'vars.php') == 'OK') {
    echo 'OK';
}
?>

Answer 2

成功时，Include_once不会返回true，如manual中所述。

你需要使用if（（包括'myfile.php'）=='OK'）{....}