Facing issue while performing file reading operations in php - php

Question

I am new to php . Currently as part of Migration activity we copied the existing php application to a new infrastructure where we are facing a strange issue.
Problem Statement:
From the php application,not able to read any file and it is not throwing any errors also. I used the following libraries and got the same behavior:
file_get_contents (This is the existing mechanism and I should use this one in the new infrastructure also)
Below two, checked to triage the issue:
readfile
fopen (tried with fopen just to see whether able to open like fopen($file, "r") or die( ),but this is also going to die condition
Issue Triaging
Made the below sample.php and make it available in my current server configuration. This is available by accessing through url (for e.g. https://myapplicationdomain/myapplication/sample.php). This php component is reading an input.txt which is in the same directory (actually this is the simulation of our problem)
<?php
ini_set('display_errors', 1); // show errors
error_reporting(-1);
//set your own error handler before the call
set_error_handler(function ($err_severity, $err_msg, $err_file, $err_line, array $err_context)
{
throw new ErrorException( $err_msg, 0, $err_severity, $err_file, $err_line );
}, E_WARNING);
echo "fopen url is";
var_dump(ini_get('allow_url_fopen'));
try{
$file ='input.txt';
if(is_readable($file)) {
echo "$file is readable \n"
} else {
echo "$file is not readable \n";
}
if(file_exists($file))
{
$homepage = file_get_contents($file);
var_dump($homepage);
echo "content is $homepage \n";
}else{
echo "file is not present \n";
}
}catch (Exception $e) {echo 'Error Caught $e';}
?>
Apache server is running using apache user and this user is having permission in the files and parent directories,
Following are the observations we got during triaging this:
When accessing through url for e.g. https://myapplicationdomain/myapplication/sample.php (i.e. through apache server).
a. functions is_readable & file_exists are returning true.
b. file_get_contents is returning blank and when I did var_dump, it is returning 'Null'
c. Confirmed the value of allow_url_fopen and it is returning 1 which is true
d. No errors are getting logged in this case.
e. Changed the permission of the 'input.txt' to see the permission behaviour. In that case,proper error got displayed in is_readable it self.So through this way ruled out the possibility of permission issue and also confirmed the error handler implementation is working fine.
f. Changed the location of input.txt to outside folders . ie. home/apache_user/ or root directory. Still file read operations are failing.
Able to run the same php code independently. i.e php sample.php .In this case,it is working as expected and all file reading operations are working fine.
3.Checked all the below php.ini configurations (removed all the values in disabled functions for testing)
a. open_basedir => no value
b. disabled_functions => no value
c. allow_url_fopen => true
Checked all the posts ,but not getting any idea how to proceed further. Following are version we are using: PHP 7.3.5 , CodeIgnitor framework and also configured php-fpm.

Answer 1

As per my understanding php library which apache was referring had some issues. Since it is a migration project and it is working fine in the current environment,copied the existing php folder (which was inside apache) and fpm binaries and configurations from the working environment to the new environment.Still not got any idea on exact root cause (as only read scenario was failing),but this got worked