moodle/lib/datalib.php

<?PHP // $Id$

/// FUNCTIONS FOR DATABASE HANDLING  ////////////////////////////////

function execute_sql($command, $feedback=true) {
/// Completely general function - it just runs some SQL and reports success.

    global $db;
    
    $result = $db->Execute("$command");

    if ($result) {
        if ($feedback) {
            echo "<P><FONT COLOR=green><B>".get_string("success")."</B></FONT></P>";
        }
        return true;
    } else {
        if ($feedback) {
            echo "<P><FONT COLOR=red><B>".get_string("error")."</B></FONT></P>";
        }
        return false;
    }
}

function modify_database($sqlfile="", $sqlstring="") {
/// Assumes that the input text (file or string consists of 
/// a number of SQL statements ENDING WITH SEMICOLONS.  The 
/// semicolons MUST be the last character in a line.
/// Lines that are blank or that start with "#" are ignored.
/// Only tested with mysql dump files (mysqldump -p -d moodle)

    global $CFG;

    $success = true;  // Let's be optimistic :-)

    if (!empty($sqlfile)) {
        if (!is_readable($sqlfile)) {
            $success = false;
            echo "<P>Tried to modify database, but \"$sqlfile\" doesn't exist!</P>";
            return $success;
        } else {
            $lines = file($sqlfile);
        }
    } else {
        $lines[] = $sqlstring;
    }

    $command = "";

    foreach ($lines as $line) {
        $line = rtrim($line);
        $length = strlen($line);

        if ($length and $line[0] <> "#") { 
            if (substr($line, $length-1, 1) == ";") {
                $line = substr($line, 0, $length-1);   // strip ;
                $command .= $line;
                $command = str_replace("prefix_", $CFG->prefix, $command); // Table prefixes
                if (! execute_sql($command)) {
                    $success = false;
                }
                $command = "";
            } else {
                $command .= $line;
            }
        }
    }

    return $success;

}

/// FUNCTIONS TO MODIFY TABLES ////////////////////////////////////////////

function table_column($table, $oldfield, $field, $type="integer", $size="10",
                      $signed="unsigned", $default="0", $null="not null", $after="") {
/// Add a new field to a table, or modify an existing one (if oldfield is defined).
    global $CFG;

    switch (strtolower($CFG->dbtype)) {

        case "mysql":
        case "mysqlt":

            switch (strtolower($type)) {
                case "integer":
                    $type = "INTEGER($size)";
                    break;
                case "varchar":
                    $type = "VARCHAR($size)";
                    break;
            }

            if (!empty($oldfield)) {
                $operation = "CHANGE $oldfield $field";
            } else {
                $operation = "ADD $field";
            }

            $default = "DEFAULT '$default'";

            if (!empty($after)) {
                $after = "AFTER `$after`";
            }

            execute_sql("ALTER TABLE {$CFG->prefix}$table $operation $type $signed $default $null $after");
            break;

        case "postgres7":        // From Petri Asikainen

            //to prevent conflicts with reserved words
            $field = "\"$field\"";
            $oldfield = "\"$oldfield\"";

            switch (strtolower($type)) {
                case "integer":
                    if ($size <= 2) {
                        $type = "INT2";
                    } 
                    if ($size <= 4) {
                        $type = "INT";
                    }
                    if  ($size > 4) {
                        $type = "INT8";
                    }
                    break;
                case "varchar":
                    $type = "VARCHAR($size)";
                    break;
            }

            $default = "DEFAULT '$default'";

            //After is not implemented in postgesql
            //if (!empty($after)) {
            //    $after = "AFTER '$after'";
            //}

            if (!empty($oldfield)) {
                execute_sql("ALTER TABLE {$CFG->prefix}$table RENAME COLUMN $oldfield TO $field");
            } else {
                execute_sql("ALTER TABLE {$CFG->prefix}$table ADD COLUMN $field $type");
            }

            /* SETTING OF COLUMN TO NULL/NOT NULL
               IS NOT POSIBLE BEFORE POSTGRESQL 7.3
               THIS COMMENTED OUT UNTIL  I FIGuRE OUT HOW GET POSTGESQL VERSION FROM ADODB

            //update default values to table
            if ($null == "NOT NULL") {
              execute_sql("UPDATE {$CFG->prefix}$table SET $field=$default where $field=NULL");
              execute_sql("ALTER TABLE {$CFG->prefix}$table ALTER COLUMN $field SET $null");
            } else {
               execute_sql("ALTER TABLE {$CFG->prefix}$table ALTER COLUMN $field DROP NOT NULL"
            }
            */
  
            execute_sql("ALTER TABLE {$CFG->prefix}$table ALTER COLUMN $field SET $default");

            break;

        default:
            switch (strtolower($type)) {
                case "integer":
                    $type = "INTEGER";
                    break;
                case "varchar":
                    $type = "VARCHAR";
                    break;
            }

            $default = "DEFAULT '$default'";

            if (!empty($after)) {
                $after = "AFTER $after";
            }

            if (!empty($oldfield)) {
                execute_sql("ALTER TABLE {$CFG->prefix}$table RENAME COLUMN $oldfield $field");
            } else {
                execute_sql("ALTER TABLE {$CFG->prefix}$table ADD COLUMN $field $type");
            }

            execute_sql("ALTER TABLE {$CFG->prefix}$table ALTER COLUMN $field SET $null");
            execute_sql("ALTER TABLE {$CFG->prefix}$table ALTER COLUMN $field SET $default");
            break;

    }
}



/// GENERIC FUNCTIONS TO CHECK AND COUNT RECORDS ////////////////////////////////////////

function record_exists($table, $field1="", $value1="", $field2="", $value2="", $field3="", $value3="") {
/// Returns true or false depending on whether the specified record exists

    global $CFG;

    if ($field1) {
        $select = "WHERE $field1 = '$value1'";
        if ($field2) {
            $select .= " AND $field2 = '$value2'";
            if ($field3) {
                $select .= " AND $field3 = '$value3'";
            }
        }
    } else {
        $select = "";
    }

    return record_exists_sql("SELECT * FROM $CFG->prefix$table $select LIMIT 1");
}


function record_exists_sql($sql) {
/// Returns true or false depending on whether the specified record exists
/// The sql statement is provided as a string.

    global $db;

    $rs = $db->Execute($sql);
    if (empty($rs)) return false;

    if ( $rs->RecordCount() ) {
        return true;
    } else {
        return false;
    }
}


function count_records($table, $field1="", $value1="", $field2="", $value2="", $field3="", $value3="") {
/// Get all the records and count them

    global $CFG;

    if ($field1) {
        $select = "WHERE $field1 = '$value1'";
        if ($field2) {
            $select .= " AND $field2 = '$value2'";
            if ($field3) {
                $select .= " AND $field3 = '$value3'";
            }
        }
    } else {
        $select = "";
    }

    return count_records_sql("SELECT COUNT(*) FROM $CFG->prefix$table $select");
}

function count_records_select($table, $select="") {
/// Get all the records and count them

    global $CFG;

    if ($select) {
        $select = "WHERE $select";
    }

    return count_records_sql("SELECT COUNT(*) FROM $CFG->prefix$table $select");
}


function count_records_sql($sql) {
/// Get all the records and count them
/// The sql statement is provided as a string.

    global $db;

    $rs = $db->Execute("$sql");
    if (empty($rs)) return 0;

    return $rs->fields[0];
}




/// GENERIC FUNCTIONS TO GET, INSERT, OR UPDATE DATA  ///////////////////////////////////

function get_record($table, $field1, $value1, $field2="", $value2="", $field3="", $value3="") {
/// Get a single record as an object

    global $CFG;

    $select = "WHERE $field1 = '$value1'";

    if ($field2) {
        $select .= " AND $field2 = '$value2'";
        if ($field3) {
            $select .= " AND $field3 = '$value3'";
        }
    }

    return get_record_sql("SELECT * FROM $CFG->prefix$table $select");
}

function get_record_sql($sql) {
/// Get a single record as an object
/// The sql statement is provided as a string.

    global $db;

    $rs = $db->Execute("$sql");
    if (empty($rs)) return false;

    if ( $rs->RecordCount() == 1 ) {
        return (object)$rs->fields;
    } else {
        return false;
    }
}

function get_record_select($table, $select="", $fields="*") {
/// Gets one record from a table, as an object
/// "select" is a fragment of SQL to define the selection criteria

    global $CFG;

    if ($select) {
        $select = "WHERE $select";
    }

    return get_record_sql("SELECT $fields FROM $CFG->prefix$table $select");
}


function get_records($table, $field="", $value="", $sort="", $fields="*") {
/// Get a number of records as an array of objects
/// Can optionally be sorted eg "time ASC" or "time DESC"
/// If "fields" is specified, only those fields are returned
/// The "key" is the first column returned, eg usually "id"

    global $CFG;

    if ($field) {
        $select = "WHERE $field = '$value'";
    } else {
        $select = "";
    }

    if ($sort) {
        $sort = "ORDER BY $sort";
    }

    return get_records_sql("SELECT $fields FROM $CFG->prefix$table $select $sort");
}

function get_records_select($table, $select="", $sort="", $fields="*") {
/// Get a number of records as an array of objects
/// Can optionally be sorted eg "time ASC" or "time DESC"
/// "select" is a fragment of SQL to define the selection criteria
/// The "key" is the first column returned, eg usually "id"

    global $CFG;

    if ($select) {
        $select = "WHERE $select";
    }

    if ($sort) {
        $sort = "ORDER BY $sort";
    }

    return get_records_sql("SELECT $fields FROM $CFG->prefix$table $select $sort");
}


function get_records_list($table, $field="", $values="", $sort="", $fields="*") {
/// Get a number of records as an array of objects
/// Differs from get_records() in that the values variable 
/// can be a comma-separated list of values eg  "4,5,6,10"
/// Can optionally be sorted eg "time ASC" or "time DESC"
/// The "key" is the first column returned, eg usually "id"

    global $CFG;

    if ($field) {
        $select = "WHERE $field in ($values)";
    } else {
        $select = "";
    }

    if ($sort) {
        $sort = "ORDER BY $sort";
    }

    return get_records_sql("SELECT $fields FROM $CFG->prefix$table $select $sort");
}



function get_records_sql($sql) {
/// Get a number of records as an array of objects
/// The "key" is the first column returned, eg usually "id"
/// The sql statement is provided as a string.

    global $db;

    $rs = $db->Execute("$sql");
    if (empty($rs)) return false;

    if ( $rs->RecordCount() > 0 ) {
        if ($records = $rs->GetAssoc(true)) {
            foreach ($records as $key => $record) {
                $objects[$key] = (object) $record;
            }
            return $objects;
        } else {
            return false;
        }
    } else {
        return false;
    }
}

function get_records_menu($table, $field="", $value="", $sort="", $fields="*") {
/// Get a number of records as an array of objects
/// Can optionally be sorted eg "time ASC" or "time DESC"
/// If "fields" is specified, only those fields are returned
/// The "key" is the first column returned, eg usually "id"

    global $CFG;

    if ($field) {
        $select = "WHERE $field = '$value'";
    } else {
        $select = "";
    }

    if ($sort) {
        $sort = "ORDER BY $sort";
    }

    return get_records_sql_menu("SELECT $fields FROM $CFG->prefix$table $select $sort");
}

function get_records_select_menu($table, $select="", $sort="", $fields="*") {
/// Get a number of records as an array of objects
/// Can optionally be sorted eg "time ASC" or "time DESC"
/// "select" is a fragment of SQL to define the selection criteria
/// Returns associative array of first two fields

    global $CFG;

    if ($select) {
        $select = "WHERE $select";
    }

    if ($sort) {
        $sort = "ORDER BY $sort";
    }

    return get_records_sql_menu("SELECT $fields FROM $CFG->prefix$table $select $sort");
}


function get_records_sql_menu($sql) {
/// Given an SQL select, this function returns an associative 
/// array of the first two columns.  This is most useful in 
/// combination with the choose_from_menu function to create 
/// a form menu.

    global $db;

    $rs = $db->Execute("$sql");
    if (empty($rs)) return false;

    if ( $rs->RecordCount() > 0 ) {
        while (!$rs->EOF) {
            $menu[$rs->fields[0]] = $rs->fields[1];
            $rs->MoveNext();
        }
        return $menu;
        
    } else {
        return false;
    }
}

function get_field($table, $return, $field, $value) {
/// Get a single field from a database record

    global $db, $CFG;

    $rs = $db->Execute("SELECT $return FROM $CFG->prefix$table WHERE $field = '$value'");
    if (empty($rs)) return false;

    if ( $rs->RecordCount() == 1 ) {
        return $rs->fields["$return"];
    } else {
        return false;
    }
}

function set_field($table, $newfield, $newvalue, $field, $value) {
/// Set a single field in a database record

    global $db, $CFG;

    return $db->Execute("UPDATE $CFG->prefix$table SET $newfield = '$newvalue' WHERE $field = '$value'");
}


function delete_records($table, $field1="", $value1="", $field2="", $value2="", $field3="", $value3="") {
/// Delete one or more records from a table

    global $db, $CFG;

    if ($field1) {
        $select = "WHERE $field1 = '$value1'";
        if ($field2) {
            $select .= " AND $field2 = '$value2'";
            if ($field3) {
                $select .= " AND $field3 = '$value3'";
            }
        }
    } else {
        $select = "";
    }

    return $db->Execute("DELETE FROM $CFG->prefix$table $select");
}


function insert_record($table, $dataobject, $returnid=true) {
/// Insert a record into a table and return the "id" field if required
/// If the return ID isn't required, then this just reports success as true/false.
/// $dataobject is an object containing needed data

    global $db, $CFG;

    // Determine all the fields needed
    if (! $columns = $db->MetaColumns("$CFG->prefix$table")) {
        return false;
    }

    $data = (array)$dataobject;

    // Pull out data from the dataobject that matches the fields in the table.
    // If fields are missing or empty, then try to set the defaults explicitly
    // because some databases (eg PostgreSQL) don't always set them properly
    foreach ($columns as $column) {
        if ($column->name <> "id") {
            if (isset($data[$column->name])) { 
                if ((string)$data[$column->name] == "" and !empty($column->has_default) and !empty($column->default_value)) {
                    $ddd[$column->name] = $column->default_value;
                } else {
                    $ddd[$column->name] = $data[$column->name];
                }
            } else {
                if (!empty($column->has_default) and !empty($column->default_value)) {
                    $ddd[$column->name] = $column->default_value;
                } 
            }
        }
    }


    // Construct SQL queries
    if (! $numddd = count($ddd)) {
        return false;
    }

    $count = 0;
    $inscolumns = "";
    $insvalues = "";
    $select = "";

    foreach ($ddd as $key => $value) {
        if (!is_null($value)){
            if ($select) {
                $inscolumns .= ", ";
                $insvalues .= ", ";
                $select .= " AND ";
            }
            $inscolumns .= "$key";
            $insvalues .= "'$value'";
            $select .= "$key = '$value'";
        }
    }

    if (! $rs = $db->Execute("INSERT INTO $CFG->prefix$table ($inscolumns) VALUES ($insvalues)")) {
        return false;
    }

    if ($returnid) {
        if ($CFG->dbtype == "mysql") { 
            return $db->Insert_ID();   // ADOdb has stored the ID for us, but it isn't reliable
        }
        
        // Try to pull the record out again to find the id.  This is the most cross-platform method.
        if ($rs = $db->Execute("SELECT id FROM $CFG->prefix$table WHERE $select")) {
            if ($rs->RecordCount() == 1) {
                return $rs->fields[0];
            }
        }

        return false;

    } else {
        return true;
    }
}


function update_record($table, $dataobject) {
/// Update a record in a table
/// $dataobject is an object containing needed data
/// Relies on $dataobject having a variable "id" to 
/// specify the record to update

    global $db, $CFG;

    if (! isset($dataobject->id) ) {
        return false;
    }

    // Determine all the fields in the table
    if (!$columns = $db->MetaColumns("$CFG->prefix$table")) {
        return false;
    }
    $data = (array)$dataobject;

    // Pull out data matching these fields
    foreach ($columns as $column) {
        if ($column->name <> "id" and isset($data[$column->name]) ) {
            $ddd[$column->name] = $data[$column->name];
        }
    }

    // Construct SQL queries
    $numddd = count($ddd);
    $count = 0;
    $update = "";

    foreach ($ddd as $key => $value) {
        $count++;
        $update .= "$key = '$value'";
        if ($count < $numddd) {
            $update .= ", ";
        }
    }

    if ($rs = $db->Execute("UPDATE $CFG->prefix$table SET $update WHERE id = '$dataobject->id'")) {
        return true;
    } else {
        return false;
    }
}




/// USER DATABASE ////////////////////////////////////////////////

function get_user_info_from_db($field, $value) {
/// Get a complete user record, which includes all the info 
/// in the user record, as well as membership information
/// Suitable for setting as $USER session cookie.

    if (!$field or !$value) {
        return false;
    }

    if (! $user = get_record_select("user", "$field = '$value' AND deleted <> '1'")) {
        return false;
    }

    // Add membership information

    if ($site = get_site()) { // Everyone is always a member of the top course
        $user->student[$site->id] = true;
    }

    if ($students = get_records("user_students", "userid", $user->id)) {
        foreach ($students as $student) {
            $user->student[$student->course] = true;
        }
    }

    if ($teachers = get_records("user_teachers", "userid", $user->id)) {
        foreach ($teachers as $teacher) {
            $user->teacher[$teacher->course] = true;
        }
    }

    if ($admins = get_records("user_admins", "userid", $user->id)) {
        foreach ($admins as $admin) {
            $user->admin = true;
            break;
        }
    }

    return $user;
}

function update_user_in_db() {
/// Updates user record to record their last access

   global $db, $USER, $REMOTE_ADDR, $CFG;

   if (!isset($USER->id)) 
       return false;

   $timenow = time();
   if ($db->Execute("UPDATE {$CFG->prefix}user SET lastIP='$REMOTE_ADDR', lastaccess='$timenow' 
                     WHERE id = '$USER->id' ")) {
       return true;
   } else {
       return false;
   }
}


function adminlogin($username, $md5password) {
/// Does this username and password specify a valid admin user?

    global $CFG;

    return record_exists_sql("SELECT u.id 
                                FROM {$CFG->prefix}user u, 
                                     {$CFG->prefix}user_admins a 
                              WHERE u.id = a.userid 
                                AND u.username = '$username' 
                                AND u.password = '$md5password'");
}


function get_site () {
/// Returns $course object of the top-level site.

    if ( $course = get_record("course", "category", 0)) {
        return $course;
    } else {
        return false;
    }
}


function get_courses($category=0, $sort="fullname ASC") {
/// Returns list of courses

    if ($category > 0) {          // Return all courses in one category
        return get_records("course", "category", $category, $sort);

    } else if ($category < 0) {   // Return all courses, even the site
        return get_records("course", "", "", $sort);

    } else {                      // Return all courses, except site
        return get_records_select("course", "category > 0", $sort);
    }
}

function get_categories() {
    return get_records("course_categories", "", "", "name");
}


function get_guest() {
    return get_user_info_from_db("username", "guest");
}


function get_admin () {
/// Returns $user object of the main admin user

    global $CFG;

    if ( $admins = get_admins() ) {
        foreach ($admins as $admin) {
            return $admin;   // ie the first one 
        }
    } else {
        return false;
    }
}

function get_admins() {
/// Returns list of all admins

    global $CFG;

    return get_records_sql("SELECT u.* 
                              FROM {$CFG->prefix}user u, 
                                   {$CFG->prefix}user_admins a
                             WHERE a.userid = u.id
                             ORDER BY u.id ASC");
}

function get_creators() {
/// Returns list of all admins

    global $CFG;

    return get_records_sql("SELECT u.*
                              FROM {$CFG->prefix}user u,
                                   {$CFG->prefix}user_coursecreators a
                             WHERE a.userid = u.id
                             ORDER BY u.id ASC");
}

function get_teacher($courseid) {
/// Returns $user object of the main teacher for a course

    global $CFG;

    if ( $teachers = get_course_teachers($courseid, "t.authority ASC")) {
        foreach ($teachers as $teacher) {
            if ($teacher->authority) {
                return $teacher;   // the highest authority teacher
            }
        }
    } else {
        return false;
    }
}

function get_course_students($courseid, $sort="u.lastaccess DESC") {
/// Returns list of all students in this course

    global $CFG;

    return get_records_sql("SELECT u.* FROM {$CFG->prefix}user u, {$CFG->prefix}user_students s
                            WHERE s.course = '$courseid' AND s.userid = u.id AND u.deleted = '0'
                            ORDER BY $sort");
}

function get_course_teachers($courseid, $sort="t.authority ASC") {
/// Returns list of all teachers in this course

    global $CFG;

    return get_records_sql("SELECT u.*,t.authority,t.role FROM {$CFG->prefix}user u, {$CFG->prefix}user_teachers t
                            WHERE t.course = '$courseid' AND t.userid = u.id AND u.deleted = '0'
                            ORDER BY $sort");
}

function get_course_users($courseid, $sort="u.lastaccess DESC") {
/// Using this method because the direct SQL just would not always work!

    $teachers = get_course_teachers($courseid, $sort);
    $students = get_course_students($courseid, $sort);

    if ($teachers and $students) {
        return array_merge($teachers, $students);
    } else if ($teachers) {
        return $teachers;
    } else {
        return $students;
    }

///    return get_records_sql("SELECT u.* FROM user u, user_students s, user_teachers t
///                            WHERE (s.course = '$courseid' AND s.userid = u.id) OR 
///                                  (t.course = '$courseid' AND t.userid = u.id)
///                            ORDER BY $sort");
}


function get_users_search($search, $sort="u.firstname ASC") {
    global $CFG;

    return get_records_sql("SELECT * from {$CFG->prefix}user 
                             WHERE confirmed = 1 
                               AND deleted = 0
                               AND (firstname LIKE '%$search%' OR 
                                    lastname LIKE '%$search%' OR 
                                    email LIKE '%$search%')
                               AND username <> 'guest' 
                               AND username <> 'changeme'");
}


function get_users_count($search="") {

    if ($search) {
        $search = " AND (firstname LIKE '%$search%'
                     OR lastname LIKE '%$search%'
                     OR email LIKE '%$search%') ";
    }

    return count_records_select("user", "username <> 'guest' AND deleted <> 1 $search");
}

function get_users_listing($sort, $dir="ASC", $page=1, $recordsperpage=20, $search="") {
    global $CFG;

    switch ($CFG->dbtype) {
        case "mysql":
             $limit = "LIMIT $page,$recordsperpage";
             break;
        case "postgres7":
             $limit = "LIMIT $recordsperpage OFFSET ".($page * $recordsperpage);
             break;
        default: 
             $limit = "LIMIT $recordsperpage,$page";
    }

    if ($search) {
        $search = " AND (firstname LIKE '%$search%'
                     OR lastname LIKE '%$search%'
                     OR email LIKE '%$search%') ";
    }

    return get_records_sql("SELECT id, username, email, firstname, lastname, city, country, lastaccess  
                              FROM {$CFG->prefix}user 
                             WHERE username <> 'guest' 
                               AND deleted <> '1' $search
                          ORDER BY $sort $dir $limit");

}

function get_users_confirmed() {
    global $CFG;
    return get_records_sql("SELECT * 
                              FROM {$CFG->prefix}user 
                             WHERE confirmed = 1 
                               AND deleted = 0
                               AND username <> 'guest' 
                               AND username <> 'changeme'");
}


function get_users_unconfirmed($cutofftime=2000000000) {
    global $CFG;
    return get_records_sql("SELECT * 
                             FROM {$CFG->prefix}user 
                            WHERE confirmed = 0
                              AND firstaccess > 0 
                              AND firstaccess < '$cutofftime'");
}


function get_users_longtimenosee($cutofftime) {
    global $CFG;

    $db->debug = true;
    return get_records_sql("SELECT u.* 
                              FROM {$CFG->prefix}user u, 
                                   {$CFG->prefix}user_students s
                             WHERE u.lastaccess > '0' 
                               AND u.lastaccess < '$cutofftime' 
                               AND u.id = s.userid
                          GROUP BY u.id");
}



/// MODULE FUNCTIONS /////////////////////////////////////////////////

function get_course_mods($courseid) {
/// Just gets a raw list of all modules in a course
    global $CFG;

    return get_records_sql("SELECT cm.*, m.name as modname
                            FROM {$CFG->prefix}modules m, {$CFG->prefix}course_modules cm
                            WHERE cm.course = '$courseid' 
                            AND cm.deleted = '0'
                            AND cm.module = m.id ");
}

function get_coursemodule_from_instance($modulename, $instance, $courseid) {
/// Given an instance of a module, finds the coursemodule description

    global $CFG;

    return get_record_sql("SELECT cm.*, m.name
                           FROM {$CFG->prefix}course_modules cm, {$CFG->prefix}modules md, {$CFG->prefix}$modulename m 
                           WHERE cm.course = '$courseid' AND 
                                 cm.deleted = '0' AND
                                 cm.instance = m.id AND 
                                 md.name = '$modulename' AND 
                                 md.id = cm.module AND
                                 m.id = '$instance'");

}

function get_all_instances_in_course($modulename, $courseid, $sort="cw.section") {
/// Returns an array of all the active instances of a particular
/// module in a given course.   Returns false on any errors.

    global $CFG;

    return get_records_sql("SELECT m.*,cw.section,cm.id as coursemodule 
                            FROM {$CFG->prefix}course_modules cm, {$CFG->prefix}course_sections cw, 
                                 {$CFG->prefix}modules md, {$CFG->prefix}$modulename m 
                            WHERE cm.course = '$courseid' AND 
                                  cm.instance = m.id AND 
                                  cm.deleted = '0' AND
                                  cm.section = cw.id AND 
                                  md.name = '$modulename' AND 
                                  md.id = cm.module
                            ORDER BY $sort");

}





/// LOG FUNCTIONS /////////////////////////////////////////////////////


function add_to_log($course, $module, $action, $url="", $info="") {
/// Add an entry to the log table.  These are "action" focussed rather
/// than web server hits, and provide a way to easily reconstruct what 
/// any particular student has been doing.
///
/// course = the course id
/// module = forum, journal, resource, course, user etc
/// action = view, edit, post (often but not always the same as the file.php)
/// url    = the file and parameters used to see the results of the action
/// info   = additional description information 

    global $db, $CFG, $USER, $REMOTE_ADDR;

    if (isset($USER->realuser)) {  // Don't log
        return;
    }

    $userid = empty($USER->id) ? "" : $USER->id;

    $timenow = time();
    $info = addslashes($info);

    $result = $db->Execute("INSERT INTO {$CFG->prefix}log (time,
                                        userid,
                                        course,
                                        ip,
                                        module,
                                        action,
                                        url,
                                        info)
                             VALUES ('$timenow',
                                        '$userid',
                                        '$course',
                                        '$REMOTE_ADDR',
                                        '$module',
                                        '$action',
                                        '$url',
                                        '$info')");

    if (!$result and ($CFG->debug > 7)) {
        echo "<P>Error: Could not insert a new entry to the Moodle log</P>";  // Don't throw an error
    }    
}


function get_logs($select, $order) {
    global $CFG;

    return get_records_sql("SELECT l.*, u.firstname, u.lastname, u.picture 
                              FROM {$CFG->prefix}log l, 
                                   {$CFG->prefix}user u 
                                   $select $order");
}

function get_logs_usercourse($userid, $courseid, $coursestart) {
    global $CFG;

    return get_records_sql("SELECT floor((`time` - $coursestart)/86400) as day, count(*) as num 
                            FROM {$CFG->prefix}log 
                           WHERE userid = '$userid' 
                             AND course = '$courseid'
                             AND `time` > '$coursestart'
                        GROUP BY day ");
}

function get_logs_userday($userid, $courseid, $daystart) {
    global $CFG;

    return get_records_sql("SELECT floor((`time` - $daystart)/3600) as hour, count(*) as num
                            FROM {$CFG->prefix}log
                           WHERE userid = '$userid' 
                             AND course = '$courseid'
                             AND `time` > '$daystart'
                        GROUP BY hour ");
}

/// GENERAL HELPFUL THINGS  ///////////////////////////////////

function print_object($object) {
/// Mostly just for debugging

    echo "<PRE>";
    print_r($object);
    echo "</PRE>";
}



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?>