Use the Google Maps API to geocode a given address.

google_geocode_api_v3.php

<?php
$url = "https://maps.googleapis.com/maps/api/geocode/xml?sensor=false&address=" . urlencode($_GET['addr']);
$ch = curl_init(); 
curl_setopt($ch, CURLOPT_URL, $url); 
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); 
$raw_xml = curl_exec($ch); 
curl_close($ch); 

$xml = new SimpleXMLElement($raw_xml);

if(is_object($xml->result->geometry->location) )
{
    echo json_encode( array('lat' => (string)$xml->result->geometry->location->lat, 'lng' => (string)$xml->result->geometry->location->lng));    
}
else
{ 
    echo json_encode(false);
}
?>