Install Sqlite3:

opkg update
opkg install sqlite3-cli
sqlite3 /mnt/sda1/sensor.db
sqlite> CREATE TABLE sensor_data(
    id INTEGER PRIMARY KEY,
    temperature VARCHAR(64),
    sqlitetimestamp DATETIME DEFAULT CURRENT_TIMESTAMP
);
sqlite> INSERT INTO sensor_data (temperature) VALUES (30);
sqlite> select * from sensor_data;
sqlite>.quit

sqlitetimestamp DATETIME DEFAULT CURRENT_TIMESTAMP, will auto CURRENT_TIMESTAMP.

Php command line:

opkg update
opkg install php5-cli php5-mod-sqlite3
nano /mnt/sda1/sensor.php
#!/usr/bin/php-cli
<?php
$db = new SQLite3('/mnt/sda1/sensor.db');
$query = "INSERT INTO sensor_data (temperature) VALUES( ".$argv[1]." )";
$db->exec($query);
$db->close();
?>
chmod 755 /mnt/sda1/sensor.php
/mnt/sda1/sensor.php 50

ATmega32u4 code:

#include <Process.h>
void setup() {
 Bridge.begin();  // Initialize Bridge
}
void loop() {
 int temperature = 50 + random(0, 5);
 Process p;              
 p.begin("/mnt/sda1/sensor.php");      
 p.addParameter(String(temperature)); 
 p.run();
 delay(5000); 
}