PHP：更改权限和所有权后文件不可写

In a PHP script , am getting below error when checked if a file is writable or not.

fopen(test.txt): failed to open stream: Permission denied

Please see blow details:

1. Apache service is running as user:apache, checked with:

   ps aux | egrep '(apache|httpd)'

2.Ownership of the file to be written and php script is changed to apache.

chown apache:apache test.txt 
chown apache:apache test.php

3.File permissions changed to:777

chmod 777 test.txt 
chmod 777 test.php

4.Tried setting: Already tried solutions provided in:fopen Permission denied on a file with 777 permissions

OS:Redhat Enterprise

Code:

<?php
echo getmyuid().':'.getmygid(); 
echo "<br/>";
echo exec('whoami');
echo "<br/>";
$dst = 'test.txt';
echo $dst, file_exists($dst) ? ' exists' : ' does not exist<br/>', "<br/>
";
echo $dst, is_readable($dst) ? ' is readable' : ' is NOT readable', "<br/>
";
echo $dst, is_writable($dst) ? ' is writable' : ' is NOT writable<br/>', "<br/>
";
$fh = fopen($dst, 'w');
if ( !$fh ) {
    echo ' last error: ';
    var_dump(error_get_last());
}

Output:

33:33
apache
test.txt exists
test.txt is readable
test.txt is NOT writable

last error: array(4) { ["type"]=> int(2) ["message"]=> string(57) "fopen(test.txt): failed to open stream: Permission denied" ["file"]=> string(34) "/var/www/data/test2.php" ["line"]=> int(10) }