At MYSQL console:

mysql> CREATE DATABASE sensors;
mysql> USE sensors;
mysql> CREATE TABLE sensor_data (
   -> id INT NOT NULL AUTO_INCREMENT,
   -> temperature INT,
   -> insert_date TIMESTAMP,
   -> PRIMARY KEY (id)
   -> );
mysql> GRANT ALL PRIVILEGES ON *.* TO 'root'@'%' IDENTIFIED BY 'password';
mysql> FLUSH PRIVILEGES;
mysql> INSERT INTO sensor_data (temperature) VALUES(20);
mysql> select * from sensor_data;
opkg update
opkg install php5-mod-mysqli
opkg install php5-cli
nano /mnt/sda1/db.php
#!/usr/bin/php-cli
<?php
$temperature = $argv[1]; 
$DBServer = '192.168.0.20'; 
$DBUser   = 'root';
$DBPass   = 'password';
$DBName   = 'sensors';  
$conn = new mysqli($DBServer, $DBUser, $DBPass, $DBName);
// check connection
if ($conn->connect_error) {
  trigger_error('Database connection failed: '  . $conn->connect_error, E_USER_ERROR);
}
$sql="INSERT INTO sensor_data (temperature) VALUES ($temperature)";
if($conn->query($sql) === false) {
  trigger_error('Wrong SQL: ' . $sql . ' Error: ' . $conn->error, E_USER_ERROR);
} 
?>
chmod 755 /mnt/sda1/db.php

Send test insert data:

/mnt/sda1/db.php  80

Arduino code:

#include <Process.h>
int temperature;
void setup() {
 Bridge.begin();  // Initialize Bridge
}
void loop() {
 int temperature = random(0, 100);
 Process p;              
 p.begin("/mnt/sda1/db.php");      
 p.addParameter(String(temperature)); 
 p.run();
 delay(5000); 
}