PSEUDOCODE: Deploy a new composer.json document

ex.php

<?php

/**
 * @param string $projectPath
 *   The basedir containing "composer.json" and "vendor".
 * @param array $composerDoc
 *   Composer specification (per composer.json).
 */
function deploy($projectPath, $composerDoc) {
  // Prepare an upgrade script
  $tmpPrefix = get_sys_tmpdir() . '/composer-deploy-' . md5(openssl_random_pseudo_bytes(32));

  $tmpJson = "{$tmpPrefix}.json";
  file_put_contents($tmpJson, json_encode($composer));

  $tmpScript = "{$tmpPrefix}.sh";
  file_put_contents($tmpScript, "
    cd $projectPath
    mv composer.json composer.json.bak
    cp $tmpJson composer.json
    if ! composer install ; then
      mv composer.json.bak composer.json
      exit 1
    fi
  ");

  // Execute the script, or ask the user to execute it.
  // Pseudocode uses switch() and echo() for brevity. Real code would be very different.
  switch (pickDeploymentStrategy()) {
    case 'exec':
      // Simple strategy. Great for local/single-user dev.
      exec($tmpScript, $output, $return);
      if ($return) echo "Error: <pre>$output</pre>"
      break;
      
    case 'ssh':
      // You'll need to either store a password or ask for a password.
      $ssh = new Net_SSH(...);
      $ssh->exec($tmpScript);
      if (...error...) echo "Error: ...";
 
    case 'prompt':
    default:
      echo "Please open the CLI and run <tt>$tmpScript</tt>."
      break;
  }

}