Arduino ethernet webclient php script and mysql

Well in my endeavour to learn Arduino Ethernet I'm still unable to get the Arduino web-client to accept commands from a server PC. Also I'm unable to get web-server to send data to a mysql database.

So I've written (probably poorly) code which I 95% understand that accepts commands from a browser.
http://192.168.1.19/?7=1 turns digital 7 on
http://192.168.1.19/?7=0 turns digital 7 off
http://192.168.1.19/?A=0 gets the value from analogue 0, prints what looks like the correct string in the web-browser but it won't write to a mysql.

#include <SPI.h>
//#include <WString.h>
#include <Ethernet.h>

byte mac[] = { 0x90, 0xA2, 0xDA, 0x00, 0x11, 0xAC }; //physical mac address
byte ip[] = { 192, 168, 1, 19 };                  // ip in lan
byte gateway[] = { 192, 168, 1, 1 };                  // internet access via router
byte subnet[] = { 255, 255, 255, 0 };                   //subnet mask
//byte server[] = { 192,168,1,20 };
Server server(80);                                      //server port
byte sampledata=50;            //some sample data - outputs 2 (ascii = 50 DEC)             
int ledPin = 4;  // LED pin
char link[]="http://www.scienceprog.com/"; //link data
String readString = String(30); //string for fetching data from address
boolean LEDON = false; //LED status flag
//#######################################
   #define READING_PIN 0
    double R1 = 10000.0; //resistance put in parallel
    double V_IN = 5.0;
    double A = 1.129148e-3;
    double B = 2.34125e-4;
    double C = 8.76741e-8;
    double K = 9.5; // mW/dec C – dissipation factor
    double SteinhartHart(double R)
    {
    // calculate temperature
    double logR  = log(R);
    double logR3 = logR * logR * logR;
    return 1.0 / (A + B * logR + C * logR3 );
    }
    int celsius;//Global declare celsius
//#######################################
void setup(){
//start Ethernet
  Ethernet.begin(mac, ip, gateway, subnet);
//pinMode;
pinMode(7,OUTPUT); digitalWrite(7,LOW);  // I use this pin as GND for the LED.
pinMode(8,OUTPUT); // Sample output, unable to use built-in LED at pin 13 because Ethernet Shield uses pins 10,11,12,13.
  
//enable serial datada print  
    Serial.begin(9600);
}
void loop(){
    readString="";//Clear readString before filling
    // Create a client connection
    Client client = server.available();
      if (client) {
      while (client.connected()) {
        if (client.available()) {
          char c = client.read();
          //read char by char HTTP request
          if (readString.length() < 30)  { 
          //store characters to string 
          readString.concat(c);
          Serial.println(readString);
          }  
          //output chars to serial port
          Serial.print(c);
            //if HTTP request has ended
            if (c == '\n') {
            //lets check if LED should be lighted
            Serial.println(readString.substring(6,9));//for test to allow readString to be viewed
              if(readString.substring(6,9)=="7=1") {//read the last 3 information characters from URL
              // Serial.println(readString);
              //set digital 7 HIGH
              Serial.println("HIGH");
             digitalWrite(7, HIGH);    // set the LED on
              readString="";//clear readString
              }
                if(readString.substring(6,9)=="7=0") {
                //set digital 7 LOW
                Serial.println("LOW");
                digitalWrite(7, LOW);    // set the LED OFF
                readString="";//clear readString           
                }
              if(readString.substring(6,9)=="A=0")  {
              //readAnal 0 temp
              ReadTemp();
              Serial.println("for test");
              client.print("GET http://192.168.1.20/update_db.php?celsius=");
              client.print(celsius);
              client.println(" HTTP/1.0");
              client.println("Host: http://192.168.1.20");
              client.println();
              readString="";//clear readString            
              } 
          
          //clearing string for next read
          readString="";
          //stopping client
          client.stop();
            }
          }
        }
      }
 }
//########################################################################
void ReadTemp() {
//Serial.print("I'm at ReadTemp ");
    double adc_raw = analogRead(READING_PIN);
    double V =  adc_raw / 1024 * V_IN;//Serial.println(adc_raw);
    double R_th = (R1 * V ) / (V_IN - V);//calculate resistance
    double kelvin = SteinhartHart(R_th) - V*V/(K * R_th);
    celsius = kelvin - 273.15;//was double but changed to int to remove decimal places
    Serial.println();
    delay(1000);
    
    return;
}
//#######################################################################

Can anyone see and explain what's wrong as I've spent all day on this with no answer.

All I want is an Arduino with Ethernet Shield that can accept commands from a web-server PC and send values to a mysql database on the same to the web-server PC.

Thanks for any help.

Tony