为什么我不能调用包含在标题中的文件中的函数？

Question

I'm using Wordpress with a custom theme.

At the top of the header.php of the theme I've got a Mobile Detect script.

require_once '/extras/Mobile_Detect.php';
$detect = new Mobile_Detect;

Then further down the header.php page I have a line that checks if the user is on a Mobile, and displays different content accordingly.

if ($detect->isMobile()) { echo "Premium"; } else { echo variable('prem_no'); }

However, in a further included PHP file further down the page, when I try to use the same script:

if ($detect->isMobile()) { echo "Find a psychic"; } else { echo "Our Psychic Readers"; }

I get this error:

Fatal error: Call to a member function isMobile() on a non-object in C:\wamp\www\clairvoyant\extraseader-categories.php on line 1

How can I make it so that a file required or included in the header.php file, can be referenced to throughout the rest of the page files?

I'm a bit confused between include, include_once, require and require_once, so can someone help clear that up?

Answer 1

Not too many differences between require and include but the main point is with require the file must exist or you get an error while include is optional.

and the _once is to make sure you don't include it more than once.

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However, in a further included PHP file further down the page, when I try to use the same script I get this error...

This sounds like $detect is not the same object for example

require_once '/extras/Mobile_Detect.php';
$detect = new Mobile_Detect;
if ($detect->isMobile()) { echo "Premium"; }//Good
....
$detect['mobile'] = 'iPhone';
if ($detect->isMobile()) { echo "Find a psychic"; }//Bad