exec（）只是在我在浏览器中访问目标php时运行

i use this code to run another php for some work (ffmpeg convert)

    $binpath = get_option('binpath','/usr/bin/php');
    $command = $binpath." -cli -f ".ABSPATH."/videocron.php";
    exec( "$command > /dev/null &", $arrOutput );

but when i upload a video and run this code don't convert video for ever.

but when i access to videocron.php from browser all videos i uploaded convert suddenly!!!

i use alternative exec function(system(); exec(); passthru(); shell_exec();) and i check videocron.php by readable function, it is readable.

even i change owner videocron.php to nobody user

in mod_security log i get this error:

[Tue Sep 20 23:01:11 2016] [error] [client 37.156.10.171] ModSecurity: Multipart parsing error (init): Multipart: Boundary not found in C-T. [hostname "codenevis.net"] [uri "/lib/upload-ffmpeg.php"] [unique_id "V@GAb38AAAEAAGrk2QoAAAAH"]

but even i unistalll mod_security it don't work automatically.

but in all don't convert video until i access to videocron.php from browser!

Thanks for huge help and help me by Patience & listening my question. i solve it by install mysqli.

yum install php-pdo php-mysqli

and restart appache