could not connect to the db: reason : SQLSTATE[HY000] [2002] No such file or directory
 

 
php -r "new PDO('mysql:hostname=localhost;dbname=test', 'username', 'password');"
SQLSTATE[HY000] [2002] No such file or directory means php cannot find the mysql.default_socket file. Fix it by modifying php.ini file. 
On Mac it is mysql.default_socket = /tmp/mysql.sock (See PHP - MySQL connection not working: 2002 No such file or directory)
SQLSTATE[HY000] [1044] Access denied for user 'username'@'localhost' CONGRATULATION! You have the correct mysql.default_socket 
setting now. Fix your dbname/username/password.
Also see Error on creating connection to PDO in PHP

You need to change host from localhost to 127.0.0.1
Laravel 4: In your app/config/database.php try changing host from localhost to 127.0.0.1
Laravel 5: In the .env file, change DB_HOST from localhost to 127.0.0.1
Source: PDOException SQLSTATE[HY000] [2002] No such file or directory
shareeditflag
 

mysqli.default_host  localhost  localhost
mysqli.default_port  3306  3306
mysqli.default_pw  no value  no value
mysqli.default_socket  /var/run/mysql/mysql.sock  /var/run/mysql/mysql.sock

CDbConnection failed to open the DB connection: SQLSTATE[HY000] [2002] No such file or directory

'connectionString' => 'mysql:unix_socket=/usr/local/LimeSurvey/var/LimeSurvey_mysqld.sock;dbname=limesurvey;',

/usr/local/LimeSurvey/var/LimeSurvey_mysqld.sock

'connectionString' => 'mysql:host=127.0.0.1;unix_socket=/usr/local/LimeSurvey/var/LimeSurvey_mysqld.sock;dbname=limesurvey;',

'connectionString' => 'mysql:host=127.0.0.1;unix_socket=/usr/local/LimeSurvey/var/LimeSurvey_mysqld.sock;dbname=limesurvey;',

Try
'connectionString' =>'mysql:host=localhost;port=3306;dbname=limesurvey;',

ln -s /usr/local/lib/mysql.sock /tmp/mysql.sock

 
<?php
if(function_exists('mysqli_connect')){
if(!($link = mysqli_connect('localhost','username','password','my_db'))){
die('could not connect: ' . mysqli_error($link));
}
} else {
die("don't have mysqli");
}
echo 'connect successfully';
mysqli_close($link);