if shortcut – no braces
                            If your if statement has only one directive, like the following:

                            if ($x) { echo “This directive”; }
                            You can drop the braces:

                            if ($x) echo “This directive”;
                        

                            if-else shortcut
                            You're probably used to the long, formal version of the if-else statement in PHP:

                            if ($x == 5) { $y = 3 } else { $y = 2 }
                            While there is nothing wrong with this statement, it's more efficient to use the shortened
                            version, using the ternary operator:

                            ($x == 5) ? $y = 3 : $y = 2;
                        

                        echo shortcut
                        echo has a shortcut too, so long as the shortcut for the PHP tag itself is supported on the
                        server. This is particularly useful if you are echoing out small snippets as variables.
                        So rather than:

                        You have chosen  widgets.
                        You can use:

                        You have chosen  widgets.
                        

                        SQL injection
                        // Escape the name.
                        $sql['name'] = mysql_real_escape_string($clean['name']);

                        // Construct the query.
                        $query = "SELECT *
                                  FROM   users
                                  WHERE  name = '{$sql['name']}'";

                        or using

                        // Provide the query format.
                        $query = $db->prepare('SELECT *
                                               FROM   users
                                               WHERE  name = :name');

                        // Provide the query data and execute the query.
                        $query->execute(array('name' => $clean['name']));
                        

                        Comparison Operators - String

                        if (strpos($authors, 'Chris') !== FALSE) {
                            echo 'Chris is an author.';
                        } else {
                            echo 'Chris is not an author.';
                        }
                        

                        Use Isset() Instead Of Strlen()

                        if (isset($username[5])) {
                            // The username is at least six characters long.
                        }