centos7 - Strange php file read and write permission problem [all 777+apache:apache]?

As mentioned, my current website directory is /var/www/html (777 permissions)
Then my
/var/www/html/g/data/visit.php file

require("../function.php");
if (file_exists($_SERVER["DOCUMENT_ROOT"]. "/cache/vc-$date.json")) {
    echo file_get_contents($_SERVER["DOCUMENT_ROOT"]. "/cache/vc-$date.json");
} else {
    $res=get_sum();
    $days1=get_days(1);
    $month=get_this_month();

    $result=["visit"=>$res,'days'=>$days1,'month'=>$month];
    $echo = json_encode($result);
    cache_this($echo,'vc-'.$date);
    echo $echo;
}

function.php

function cache_this($result,$name){//内容，命名规则
  //file_put_contents("/cache/$name.json", $result)or die("Unable to open file!");

    $myfile = fopen($_SERVER['DOCUMENT_ROOT']."/cache/$name.json", "w") or die("Unable to open file!");
    $txt = $result;
    fwrite($myfile, $txt);
    fclose($myfile);
}

This is part of the result of my ls -l

-rwxrwxrwx.  1 root   root        81 11月  4 2013 bottom.php
drwxrwxrwx.  2 apache apache    4096 11月 10 17:09 cache

Then I looked at the user and group in httpd.conf, and they were all correct for apache.
But the json file just couldn’t be written into the cache folder, and $myfile always returned false.
Please tell me what the problem is. I have been struggling all night. The Double Eleven centos discussion group is full of troubles and I can’t find out what is going on...
Urgent request……………… (powerless

Reply content:

As mentioned, my current website directory is /var/www/html (777 permissions)
Then my
/var/www/html/g/data/visit.php file

require("../function.php");
if (file_exists($_SERVER["DOCUMENT_ROOT"]. "/cache/vc-$date.json")) {
    echo file_get_contents($_SERVER["DOCUMENT_ROOT"]. "/cache/vc-$date.json");
} else {
    $res=get_sum();
    $days1=get_days(1);
    $month=get_this_month();

    $result=["visit"=>$res,'days'=>$days1,'month'=>$month];
    $echo = json_encode($result);
    cache_this($echo,'vc-'.$date);
    echo $echo;
}

function.php

function cache_this($result,$name){//内容，命名规则
  //file_put_contents("/cache/$name.json", $result)or die("Unable to open file!");

    $myfile = fopen($_SERVER['DOCUMENT_ROOT']."/cache/$name.json", "w") or die("Unable to open file!");
    $txt = $result;
    fwrite($myfile, $txt);
    fclose($myfile);
}

This is part of the result of my ls -l

-rwxrwxrwx.  1 root   root        81 11月  4 2013 bottom.php
drwxrwxrwx.  2 apache apache    4096 11月 10 17:09 cache

Then I looked at the user and group in httpd.conf, and they were all correct for apache.
But the json file just couldn’t be written into the cache folder, and $myfile always returned false.
Please tell me what the problem is. I have been struggling all night. The Double Eleven centos discussion group is full of troubles and I can’t find out what is going on...
Urgent request……………… (powerless

View SELinux status

Why do you have to write to the root directory? Can’t the current directory work?