This Phing tasks will read a PHP variable from a PHP file, allowing it to be output as a Phing property.

PhpVariableTask.php

<?php

/**
 * Class PhpVariableTask
 *
 * This task allows php variables from php files to be output into Phing
 * properties.
 */
class PhpVariableTask extends Task {

  /**
   * The PHP file from which to read the variable.
   * @var string
   */
  protected $file = NULL;

  /**
   * The PHP variable name. This may be a nested array.
   * @var string
   */
  protected $variable = NULL;

  /**
   * Property name to set with output value.
   * @var string
   */
  private $outputProperty;

  public function init() {}

  public function main()
  {
    require $this->file;

    // @see http://php.net/manual/en/language.variables.variable.php
    $variable = $this->variable;

    // If variable is an array, parse array keys from string. Example value
    // would be databases[default][default][database].
    if (strstr($variable, '[')) {
      // Split string parts.
      $keys = preg_split('~(])?(\\[|$)~', $variable, -1, PREG_SPLIT_NO_EMPTY);

      // Determine the variable name. E.g., $database is variable in example.
      $variable_name = array_shift($keys);
      $value = $$variable_name;

      // Loop through nested array keys.
      foreach ($keys as $key)
      {
        if (!is_array($value) || !array_key_exists($key, $value)) {
          $value[$key] = NULL;
        }
        $value = &$value[$key];
      }
    }
    // If this is not an array, simply take variable value.
    else {
      $value = $$variable;
    }

    if (null !== $this->outputProperty) {
      $this->project->setProperty($this->outputProperty, $value);
    }

  }

  /**
   * Sets $this->file property.
   *
   * @param string $file
   *   The PHP file from which to read the variable.
   */
  public function setFile($file)
  {
    $this->file = $file;
  }

  /**
   * Sets $this->variable
   *
   * @param string $variable
   *   The PHP variable name. This may be a nested array.
   */
  public function setVariable($variable)
  {
    $this->variable = $variable;
  }

  /**
   * Sets $this->outputProperty property.
   *
   * @param string $prop
   *   The name of the Phing property whose value to set.
   */
  public function setOutputProperty($prop)
  {
    $this->outputProperty = $prop;
  }
}

Example usage:

  <!-- Extract PHP variable values from local.settings.php. -->
  <property name="local.settings.file" value="${repo.root}/sites/default/settings/local.settings.php" />
  <!-- Extracts value of $base_url and outputs to local_url property in Phing. -->
  <phpVariable file="${local.settings.file}" variable="base_url" outputProperty="local_url" />
  <!-- Extracts values from the $databases array and outputs to db.* properties. -->
  <phpVariable file="${local.settings.file}" variable="databases[default][default][database]" outputProperty="db.database" />
  <phpVariable file="${local.settings.file}" variable="databases[default][default][username]" outputProperty="db.username" />
  <phpVariable file="${local.settings.file}" variable="databases[default][default][password]" outputProperty="db.password" />
  <phpVariable file="${local.settings.file}" variable="databases[default][default][host]" outputProperty="db.host" />
  <phpVariable file="${local.settings.file}" variable="databases[default][default][port]" outputProperty="db.port" />