Shell script for switching php version

phpswitch.sh

#!/bin/bash
## Switch php version
## Command line need only one argument, it's php version 

exists()
{
  command -v "$1" >/dev/null 2>&1
}

##< Allowed only for admin
if ! [ $(id -u) = 0 ]; then
   echo "The script need to be run as root." >&2
   exit 1
fi

##< Check existing parameters
if [ $# -gt 0 ]; then

    if exists "php$1"; then
      echo 'This version php exists!'
      echo "Starting switching to php$1..."

      ##< Unlinking the old PHP version
      if [ -f /usr/bin/php ]; then
        unlink /usr/bin/php
      fi;
      unlink /etc/alternatives/php

      ##< Linking new PHP version
      ln -s /usr/bin/php$1 /etc/alternatives/php
      if ! [ -f /usr/bin/php ]; then
        ln -s /etc/alternatives/php /usr/bin/php
      fi;

      echo "PHP version have switched:"
      php -v
      exit 0

    else
      echo 'Your system does not have this php version. Firstly install it...'
    fi

else
    echo "Your command line contains no arguments, specify version of php..."
fi