Error in Installer.php

Hello Team,

I had started migrating my site from 1 hosting to another.
but it got stuck at the step number 3.
Now when I am trying to start the process again from step 1.
It is showing me this error in installer.php
I had delted all the files created in the filemanager at my 1st attempt and also the Db.

[PHP ERR][FATAL] MSG:Uncaught Error: Call to undefined function json_encode() in /home/promomeds/public_html/installer.php:1669
Stack trace:
#0 /home/promomeds/public_html/installer.php(1521): DUPX_CSRF::saveCSRFVars(Array)
#1 /home/promomeds/public_html/installer.php(1556): DUPX_CSRF::setKeyVal('_DUPX_CSRF_step...', '21F516B83E2CC18...')
#2 /home/promomeds/public_html/installer.php(1683): DUPX_CSRF::generate('step1')
#3 {main}
  thrown [CODE:1|FILE:/home/promomeds/public_html/installer.php|LINE:1669]

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