If you say it works on the terminal and not on apache then apache's php.ini file may be disabling the use of shell_exec().

See http://www.php.net/manual/en/ini.core.php#ini.disable-functions

Your apache's php.ini file may look something like

disable_functions=exec,passthru,shell_exec,system,proc_open,popen

Remove shell_exec from this list and restart the web server, although this is a security risk and I don't recommend it.

Answer from SamV on Stack Overflow
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PHP
php.net › manual › en › function.shell-exec.php
PHP: shell_exec - Manual
... If you're trying to run a command such as "gunzip -t" in shell_exec and getting an empty result, you might need to add 2>&1 to the end of the command, eg: Won't always work: echo shell_exec("gunzip -c -t $path_to_backup_file"); Should work: ...
Top answer
1 of 6
12

The Apache’s user www-data need to be granted privileges to execute certain applications using sudo.

  1. Run the command sudo visudo. Actually we want to edit the file in etc/sudoers.To do that, by using sudo visudo in terminal ,it duplicate(temp) sudoers file to edit.
  2. At the end of the file, add the following ex:-if we want to use command for restart smokeping and php command for another action in your question,

www-data ALL=NOPASSWD: /etc/init.d/smokeping/restart, usr/bin/php

(This is assuming that you wish to run restart and php commands using super user (root) privileges.And you use php command in usr/bin/ path )

However, if you wish to run every application using super user privileges, then add the following instead of what’s above.You might not want to do that, not for ALL commands, very dangerous.

www-data ALL=NOPASSWD: ALL

3.After edit the sudoers file(by visudo we edit the temp file of sudoers so save and quit temp file(visudo) to write in sudoers file.(wq!)

4.That’s it, now use exec() or shell_exec in the following manner inside your xxx.phpscript.keep remember to use sudo before the command use in the php script.

ex:-

exec ("sudo /etc/init.d/smokeping restart 2>&1");

or

shell_exec("sudo php -v"); 

So in your problem,add the commands that you wish to use in to the step no (2.) as I add and change your php script as what you want.

here is the same problem as yours https://stackoverflow.com/a/22953339/1862107

2 of 6
5

Try specifying the entire path to the php binary.. Eg, /usr/bin/php

If you don't know it, find it using: which php

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Reddit
reddit.com › r/phphelp › shell_exec not working
r/PHPhelp on Reddit: Shell_Exec not working
November 5, 2021 -

Hello,
I have a php script that execute a Shell. It is supposed to execute a .ps1 when i request the page.
It was working fine but a coworker had to reboot the IIS VM running php 8 with CGI. The script is not working anymore and is giving me a blank page when i request it.

<?php echo Shell_exec ('Powershell.exe -ExecutionPolicy Bypass -NoProfile -File ".\dev.ps1"'); ?>

What i did so far :

  • Checking the php.ini file to make sure Shell_exec wasn't in Disable_functions="".

  • Changing the FastCGI Protocol configuration from "Named pipe" to "TCP"

  • Rebooting, of course

Thanks,

🌐
Reddit
reddit.com › r/phphelp › php shell_exec not working with pipes
r/PHPhelp on Reddit: php shell_exec not working with pipes
May 28, 2022 -

Hi all I'm trying to SvtAv1EncApp tools via web interface, I try to us both exec() shell_exec() with no success , BTW I print the command and run it into the shell directly and it's works perfectly fine.

$cmd2="/usr/local/bin/ffmpeg -loglevel -8 -i "$mp4" -s 960x540 -strict -1 -f yuv4mpegpipe - | /usr/local/bin/SvtAv1EncApp --no-progress -i stdin --rc 0 -q 38 --preset 8 -b stdout 2>/var/www/vl/ffmpeg.log | /usr/local/bin/ffmpeg -loglevel -8 -y -i - -i "$mp4" -map 0:v -map 1:a:0 -c:v copy $a '".$mpa."_.mkv' & ";

shell_exec( $cmd2 ) ;

Here is the text of echo $cmd2 output

/usr/local/bin/ffmpeg -loglevel -8 -i "FHD.mp4" -s 960x540 -strict -1 -f yuv4mpegpipe - | /usr/local/bin/SvtAv1EncApp --no-progress -i stdin --rc 0 -q 38 --preset 8 -b stdout 2>/var/www/vl/ffmpeg.log | /usr/local/bin/ffmpeg -loglevel -8 -y -i - -i "FHD.mp4" -map 0:v -map 1:a:0 -c:v copy -strict -2 -c:a libopus -b:a 64k 'FHD_.mkv' &

=Update=

I kinda solve it , I don't know why but exec() successfully executed the script , I created new bash script from command line thanks to @xisonc suggesting nano /usr/local/sbin/av1c with this value

!/bin/sh

touch /var/www/vl/ffmpeg.log /usr/local/bin/ffmpeg -loglevel -8 -i "$1" -s 960x540 -strict -1 -f yuv4mpegpipe -
| /usr/local/bin/SvtAv1EncApp --no-progress -i stdin --rc 0 -q 38 --preset 8 -b stdout 2>/var/www/vl/ffmpeg.log
| /usr/local/bin/ffmpeg -loglevel -8 -y -i - -i "$1" -map 0:v -map 1:a:0 -c:v copy -strict -2 -c:a libopus -b:a 64k "$2"

On the php script i had this

$cmd2="/usr/local/sbin/av1c '$mp4' '$mpa"."_.mkv'   2>/dev/null >/dev/null & " ; 
exec( $cmd2 , $pid, $r )    ;   
var_dump(  $r )                ;

var_dump returns 0 , and since the bash script are silent I don't need to see the output , now I want to change it to wok on the background it's running on background now after adding 2>/dev/null >/dev/null & at the end of the command .

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Stack Overflow
stackoverflow.com › questions › 42041565 › shell-exec-command-in-php-not-working-properly
shell exec - shell_exec command in php not working properly - Stack Overflow
February 6, 2017 - [akshay@gold tmp]$ cat test.php <?php $query = "/tmp/./a.out /var/www/project/constraints.txt /var/www/project/constraints_keyword.txt /var/www/project/FIB.txt /var/www/project/ANS.txt"; $var = shell_exec($query); echo $var; ?> ... [akshay@gold tmp]$ php test.php Arg[0] = /tmp/./a.out Arg[1] = /var/www/project/constraints.txt Arg[2] = /var/www/project/constraints_keyword.txt Arg[3] = /var/www/project/FIB.txt Arg[4] = /var/www/project/ANS.txt ... Its working if we run the php file on the terminal but its not working for the browser..
Find elsewhere
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Unix.com
unix.com › unix for beginners q & a
Shell_exec is not working - UNIX for Beginners Q & A - Unix Linux Community
September 20, 2019 - I am trying to execute a command with shell_exec but this command does not work, other commands work <?php $output = shell_exec("tail /var/log/syslog"); echo "<pre>$output</pre>"; ?>
Top answer
1 of 2
3

There's multiple problems here.

  1. Do people even read the error messages they get?
  2. Don't use shell commands to read a file to a variable! Use fopen.
  3. Don't do globbing. Globs are expanded by the shell, but PHP is not a shell, so it doesn't do globbing. It hands your exact command off to the shell, and asks the shell to execute it. And yes, *-release is a valid filename.
    [~]$ ls -la /tmp/\*-releases 
    -rw-r--r-- 1 vidarlo users 0 Jun 23 10:16 /tmp/*-releases
    [~]$ 
  1. Globbing potentially opens you to attacks. If you glob, you have no control over what files you end up reading. That's a potential security issue. Probably not in this case, as you're reading from /etc, but...
  2. You lack a basic understanding about your environment, when you expect that modifying a path parameter will change anything - the problem is not that cat command is not found, it's that the file you give as parameter is not found... A general understanding of the platform is a good starting point for programming.
  3. putenv('/etc'); is not how putenv works. Environment variables are generally key=value-pairs.
  4. Don't post it on serverfault. It's not about managing IT, it's purely about programming. Additionally, you should probably spend some time to learn the platform you're working on.
2 of 2
0

The problem was that PHP was setup to run in chroot jail. I had exhausted all other possibilities. I only even discovered it thanks to @vidarlo's comment.

I was able to resolve the issue in WHM via the CageFS plugin. The Linux user that PHP uses was set to execute and I removed it from the association.

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OpenLiteSpeed
forum.openlitespeed.org › home › forums › community support › linux support: debian, ubuntu, solusos etc
I can't do shell_exec using PHP | OpenLiteSpeed Community and News
May 29, 2020 - <?php $command = escapeshellcmd('python3 /opt/test.py'); $output = shell_exec($command); echo $output; ?> `cat /opt/test.py` ... Hello World It seems working fine from my test. Please confirm if this is a valid testing to you. Best, Eric · You must log in or register to reply here.
Top answer
1 of 1
6

By the looks of it your PATH variable only includes /bin. This only allows you to run executables within that directory. There are a few ways to fix this.

Method 1: Configure the web server environment varibles

If you are running apache, you can simply edit /etc/apache2/envvars to include a PATH varibale definition. Edit the file and add a new line to the bottom (if it doesn't already exist):

# /etc/apache2/envvars
...

export PATH="/bin:/usr/local/bin"

Method 2: Configure the PATH for the user

Alternatively, if you are running the web server as a user other than a service user, that user may not have their PATH properly configured. This is as simple as changing their environment variables for the user and the web server will inherit it (unless defined otherwise in the web server's configuration).

First step is figure out which user your web server is running as. If you don't know, you can check list the running processes to find the user. This can be accomplished by running the following command:

ps aux|grep {webserver}|grep -v grep Where {webserver} is replaced with the web server you are currently running. (apache/httpd, nginx)

Alternatively, you can check in of the following config files:

  • /etc/httpd/conf/httpd.conf - CentOS Apache
  • /etc/apache2/apache2.conf - Ubuntu/Debian Apache
  • /etc/nginx/nginx.conf - nginx config

(There are many other possible configurations, but these are the most common)

Once you've found out which user you're running as, you will need to then set the PATH variable for that user. This could be as simple as exporting the PATH in their home bash configuration. This could be /home/bob/.bashrc for example. Service users without a home will be different however.

Method 3: Declare the PATH within your PHP script

You can manually specify the PATH variable within your PHP script. This can be accomplished by adding the following line to your script:

<?php

putenv('PATH=/bin:/usr/local/bin');
...

You will need to change the PATH to suit your needs, and it will need to be declared before you call shell_exec().

This method isn't preferred as you will need to specify this for each PHP script you execute that makes use of the shell_exec() call to binaries outside of /bin, but it is a quick one off solution that will work.

More importantly, you are writing code that is not portable and is dependent on a specific system. This is bad coding practice and is not recommended/frowned upon.

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CyberPanel Community
community.cyberpanel.net › support and discussion › general discussion
PHP exec() not working | php.ini is fine - General Discussion - CyberPanel Community
March 7, 2023 - Hi, I’ve seen few topics but nothing worked. My php.ini doesn’t block exec() or shell_exec(), but yet the shell command from php doesn’t execute. It works only from the terminal. I gave folder permissions to user: cy…
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BCCNsoft
doc.bccnsoft.com › docs › php-docs-7-en › function.shell-exec.html
shell_exec
This function can return NULL both when an error occurs or the program produces no output. It is not possible to detect execution failures using this function. exec() should be used when access to the program exit code is required. ... This function is disabled when PHP is running in safe mode.
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Super User
superuser.com › questions › 781412 › unable-to-start-bash-script-with-shell-exec
linux - Unable to start bash script with shell_exec - Super User
I've been googling and trying to solve this problem with my php script for a few days now and I'm hoping someone here can see the problem I'm missing in getting my php script to kick off my bash script. ... //kickoff the yapeal script echo "Starting yapeal.sh<br>"; echo "Current working directory: "; echo getcwd() . "\n"; shell_exec('./yapeal.sh'); echo "<br>yapeal.sh ran, I hope.<br>";
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GeeksforGeeks
geeksforgeeks.org › php › php-shell_exec-vs-exec-function
PHP shell_exec() vs exec() Function - GeeksforGeeks
July 11, 2025 - Note: This function is disabled when PHP is running in safe mode. Example: In this example we use the shell_exec() function to execute the ls command, listing files and directories.