cv2 unable to access video when called with php

I have written a code where I assign a video file to the cv2 module in python script. I am running this python script with PHP. when I run the PHP in the terminal then cv2 can access the video, but when I run the PHP on the webpage then cv2 cannot access the video.

python filename - video2frames.py

PHP filename - script.php

bootscript.php -

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>script</title>
</head>
<body>
    
    <?
        $out = shell_exec("python3 video2frames.py");
        echo "$out";

    ?>

video2frames.py -

# Importing all necessary libraries 
import sys
import os 
import cv2

value = 'cv2' in sys.modules
print('Check if true cv2 is imported',value)

# Read the video from specified path 
cam = cv2.VideoCapture('video.mp4') 
print('cam value : ',cam)

output in terminal -

[customro@heimdall www]$ php bootscript.php
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>script</title>
</head>
<body>

    Check if true cv2 is imported True
cam value :  <VideoCapture 0x7f2731224fd0>

</body>
</html>

output in webpage -

Check if true cv2 is imported True cam value :

I Have tried -

1. changing permissions of all the files associated with this program to 777
2. I have tried exec, system, shell_exec commands to call python file in PHP