snippet-from-class-freemius.php

<?php

private function _find_caller_plugin_file() {
    $bt                      = debug_backtrace();
    $abs_path_lenght         = strlen( ABSPATH );
    $backtrace_entries_count = count( $bt );
    $plugin_file             = null;

    for ( $i = 1; $i < $backtrace_entries_count; $i++ ) {
        if ( false !== strpos( substr( fs_normalize_path( $bt[ $i ]['file'] ), $abs_path_lenght ), '/freemius/' ) ) {
            continue;
        }

        if ( ! in_array( $bt[ $i ]['function'], array( 'freemius', 'fs_init', 'fs_dynamic_init' ) ) ) {
            continue;
        }

        if ( basename( dirname( $bt[ $i ]['file'] ) ) !== $this->_slug ) {
            continue;
        }

        $plugin_file = $bt[ $i ]['file'];

        break;
    }

    return $plugin_file;
}