Can't get result with file_exists()

Question

I've been trying to delete a .json file with php on my site, and can't get it to work. It seems I can't get the path to the file right, or it's invisible. So I thought I'd check with file_exists(), and no matter what I try, I cannot get the system to see a file that is on my server.

the json folder exists in this path /mytheme/assets/js/geofences/1069.json

The php is being run from this path /mytheme/inc/filelookingforjson.php

I have tried "../assets/js.." to send path pointer up one level using relative path...

I have tried absolute filepaths. and it's behaving like the file isn't there. Is there some htaccess or some other thing i need to do on a wordpress site? Permissions on the geofences folder are set to read, writeable etc... the code below sends me an email saying there is no file. I'm sure I have the path wrong, if i can get this correct than i can work on the unlink... thank you for any input.

$file = '/wp-content/themes/mytheme/assets/js/geofences/1069.json';

    if(file_exists($file)){
    mail("me@email.com","file exists","file name is there");    
    } else {me@email.com","file does not exist found","file name is 
 not there");
}

Answer 1

The issue

If the folder structure is:

mytheme/
  inc/
    filelookingforjson.php
  assets/
    js/
      geofences/
        1069.json

then the path to the json file from the PHP file would be:

../assets/js/geofences/1069.json

However, considering that your PHP file most likely gets included by other PHP files, the path will be relative from the first accessed PHP file.

Why is this?

Imagine this file structure:

index.php
folder/
   foo.php
   subfolder/
      bar.php
assets/
    hello.txt

Let's say that you want to read the file hello.txt in the file bar.php , then the relative path to hello.txt would be ../../assets/hello.txt . This would work if you run the file bar.php directly.

The gotcha

The "gotcha" is when you're not accessing bar.php directly.

Let's now say that index.php includes foo.php and foo.php includes bar.php .

If you run index.php , the relative path in bar.php won't work anymore since it isn't relative from the first accessed PHP file in the include chain, which is index.php .

This does make sense if you think of include and require as a "copy/paste". PHP "copys" the code from the included file and "pastes" it into the file that does the including.

Note: this is of course a simplification of how it actually works

Solution

The magic constant __DIR__ .

If you add that before your relative path, PHP will replace it with the absolute path to the file it was written in.

The code:

$file = __DIR__ . '/../../assets/hello.txt';

will be read by PHP as:

$file = '/folder/subfolder/../../assets/hello.txt'; 

Now it won't matter what file includes bar.php since the path will stay absolute.

The same thing goes when you're trying to include files using relative paths.

On a real server, the absolute path would probably look something like /path/from/the/file-systems/root/folder/assets/hello.txt .