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POET Coding Standard

Looping Over Slow Functions

Usage of slow functions from within loops could lead to performance problems. Often times, database queries in loops can be removed from the loop and rewritten to grab the data in a single query.

Built In Database Methods

Moodle comes with its own database layer. The base class is moodle_database and it is accessed by the $DB global variable. This layer takes care of supporting various database backends. All interactions with the database must go through this class.

Database Table Prefix

SQL written for Moodle should not include the table prefix. The table name should just be passed into the moodle_database class method or if using raw SQL, the table name should be surrounded by curly brackets.

Valid: Not using the prefix. Invalid: Using the prefix. 
$DB->get_records('user', ['id' => 1]);
$DB->get_records_sql('SELECT * FROM {user} WHERE id = ?', [1]);

$DB->get_records('mdl_user', ['id' => 1]);
$DB->get_records_sql('SELECT * FROM mdl_user WHERE id = ?', [1]);
## Request Variables Some request variables are not reliable or have been removed in later versions of PHP. Usage of them should be avoided. ## Deprecated Parameter Constants The constants prefixed with *PARAM_* within Moodle are used for cleaning parameters. Deprecated constants should not be used. Always try to use the most specific constant possible, EG: PARAM_TEXT instead of PARAM_CLEAN. ## Modifying PHP Configuration Settings Cannot use the *ini_set* PHP function. This can cause unexpected behavior.
Valid: Use Moodle method to modify PHP settings. Invalid: Directly calling ini_set. 
raise_memory_limit(MEMORY_HUGE);

ini_set('memory_limit', '1G');
## Superglobals Not allowed to read values from PHP superglobals like *$_GET*, *$_POST*, etc.
Valid: Use Moodle methods to access request data. Invalid: Use of $_GET. 
$id = required_param('id', PARAM_INT);
$action = optional_param('action', 'default', PARAM_ALPHANUMEXT);

$id = $_GET['id'];
$action = !empty($_GET['action']) ? $_GET['action'] : 'default';
## Warn About Raw SQL Functions Moodle provides a number of helper functions for accessing the database, including some functions that allow the use of raw SQL. This can be problematic if the SQL is complext, inefficient, or includes parameters correctly. For this reason, this sniff warns about the use of these functions for further investigation.
Valid: Use placeholders for parameters. Invalid: Using string concatenation for parameters. 
$DB->get_records_sql('SELECT * FROM {course} WHERE shortname = ?', [$get]);

$DB->get_records_sql('SELECT * FROM {course} WHERE shortname = '.$get);
Valid: Make use of indexes when dealing with large data sets. Invalid: There is no index on just username. 
$DB->get_records_sql('
    SELECT c.*
      FROM {user_enrolments} ue
      JOIN {enrol} e ON e.id = ue.enrolid
      JOIN {course} c ON e.courseid = c.id
      JOIN {user} u ON ue.userid = u.id
     WHERE u.username = ?
       AND u.mnethostid = ?
', [$USER->username, $CFG->mnet_localhost_id]);

$DB->get_records_sql('
    SELECT c.*
      FROM {user_enrolments} ue
      JOIN {enrol} e ON e.id = ue.enrolid
      JOIN {course} c ON e.courseid = c.id
      JOIN {user} u ON ue.userid = u.id
     WHERE u.username = ?
', [$USER->username]);
## Manual Inclusion of jQuery Including jQuery and associated libraries manually can cause issues. The versions bundled with Moodle should be used.
Valid: Use Moodle's JQuery library. Invalid: Using your own JQuery library. 
$PAGE->requires->jquery();

$PAGE->requires->js('/mod/foo/jquery.js');
## Unconditional If Statements If statements that are always evaluated should not be used.
Valid: An if statement that only executes conditionally. Invalid: An if statement that is always performed. 
if ($test) {
    $var = 1;
}

if (true) {
    $var = 1;
}
Valid: An if statement that only executes conditionally. Invalid: An if statement that is never performed. 
if ($test) {
    $var = 1;
}

if (false) {
    $var = 1;
}
## Todo Comments FIXME Statements should be taken care of.
Valid: A comment without a fixme. Invalid: A fixme comment. 
// Handle strange case
if ($test) {
    $var = 1;
}

// FIXME: This needs to be fixed!
if ($test) {
    $var = 1;
}
## Todo Comments TODO Statements should be taken care of.
Valid: A comment without a todo. Invalid: A todo comment. 
// Handle strange case
if ($test) {
    $var = 1;
}

// TODO: This needs to be fixed!
if ($test) {
    $var = 1;
}
## Byte Order Marks Byte Order Marks that may corrupt your application should not be used. These include 0xefbbbf (UTF-8), 0xfeff (UTF-16 BE) and 0xfffe (UTF-16 LE). ## Multiple Statements On a Single Line Multiple statements are not allowed on a single line.
Valid: Two statements are spread out on two separate lines. Invalid: Two statements are combined onto one line. 
$foo = 1;
$bar = 2;

$foo = 1; $bar = 2;
## Space After Casts Spaces are not allowed after casting operators.
Valid: A cast operator is immediately before its value. Invalid: A cast operator is followed by whitespace. 
$foo = (string)1;

$foo = (string) 1;
## Lowercase Keywords All PHP keywords should be lowercase.
Valid: Lowercase array keyword used. Invalid: Non-lowercase array keyword used. 
$foo = array();

$foo = Array();
## Line Endings Unix-style line endings are preferred ("\n" instead of "\r\n"). ## Deprecated Functions Deprecated functions should not be used.
Valid: A non-deprecated function is used. Invalid: A deprecated function is used. 
$foo = explode('a', $bar);

$foo = split('a', $bar);
## PHP Code Tags Always use <?php ?> to delimit PHP code, not the <? ?> shorthand. This is the most portable way to include PHP code on differing operating systems and setups. ## Silenced Errors Suppressing Errors is not allowed.
Valid: isset() is used to verify that a variable exists before trying to use it. Invalid: Errors are suppressed. 
if (isset($foo) && $foo) {
    echo "Hello\n";
}

if (@$foo) {
    echo "Hello\n";
}
## Closing PHP Tags Files should not have closing php tags.
Valid: No closing tag at the end of the file. Invalid: A closing php tag is included at the end of the file. 
<?php
$var = 1;

<?php
$var = 1;
?>
Documentation generated on Fri, 10 Jun 2016 12:59:10 -0700 by [PHP_CodeSniffer 2.6.0](https://github.com/squizlabs/PHP_CodeSniffer)