1 install.core.inc install_verify_requirements(&$install_state)

Verifies the requirements for installing Backdrop.


$install_state: An array of information about the current installation state.

Return value

string|NULL: A themed status report, or an exception if there are requirement errors. If there are only requirement warnings, a themed status report is shown initially, but the user is allowed to bypass it by providing 'continue=1' in the URL. Otherwise, no output is returned, so that the next task can be run in the same page request.




core/includes/install.core.inc, line 767
API functions for installing Backdrop.


function install_verify_requirements(&$install_state) {
  // Check the installation requirements for Backdrop and this profile.
  $requirements = install_check_requirements($install_state);

  // Verify existence of all required modules.
  $requirements += backdrop_verify_profile($install_state);

  // Check the severity of the requirements reported.
  $severity = backdrop_requirements_severity($requirements);

  // If there are errors, always display them. If there are only warnings, skip
  // them if the user has provided a URL parameter acknowledging the warnings
  // and indicating a desire to continue anyway.
  // @see backdrop_requirements_url().
  if ($severity == REQUIREMENT_ERROR || ($severity == REQUIREMENT_WARNING && empty($install_state['parameters']['continue']))) {
    if ($install_state['interactive']) {
      backdrop_set_title(st('Requirements problem'));
      $status_report = st('Resolve the problems and <a href="!url">try again</a>.', array('!url' => check_url(backdrop_requirements_url($severity))));
      $status_report .= '<br><br>';
      $status_report .= theme('status_report', array('requirements' => $requirements, 'phase' => 'install'));
      return $status_report;
    else {
      // Throw an exception showing any unmet requirements.
      $failures = array();
      foreach ($requirements as $requirement) {
        // Skip warnings altogether for non-interactive installations; these
        // proceed in a single request so there is no good opportunity (and no
        // good method) to warn the user anyway.
        if (isset($requirement['severity']) && $requirement['severity'] == REQUIREMENT_ERROR) {
          $failures[] = $requirement['title'] . ': ' . $requirement['value'] . "\n\n" . $requirement['description'];
      if (!empty($failures)) {
        throw new Exception(implode("\n\n", $failures));

  // Non-interactive requirements check.
  return NULL;