Php

<input type="text" id="champ1">
<input type="text" id="champ2">

<script language="javascript">
function fillField ( inputFieldName, outputFieldName ){
   if ( document.getElementById(inputFieldName) &&  document.getElementById(outputFieldName) ){
      // --- Set value from input field to output field
      document.getElementById(outputFieldName).value = document.getElementById(inputFieldName).value;
      // --- Get focus to the output field
      document.getElementById(outputFieldName).focus();
   }
}
</script>

<input type="text" id="champ1" onMouseOver="fillField('champ1','champ2')">
<input type="text" id="champ2">

<?php

//------------------------------------------\\
function db_connect(){
//------------------------------------------\\
	$base ="users";
	$conn = mysql_connect('localhost','root','');
	if(!$conn)
		messerr("Pb connection mysql","white");

	if(!mysql_select_db($base,$conn)){
		mysql_close($conn);
		messerr("Pb connection a la base \"".$base."\"","white");
	}
	return $conn;
}

function deconnect($conn,$nb){
	mysql_close($conn);
	return $nb;
}

function messerr ( $lib, $val )
{
	echo "<SCRIPT LANGUAGE=\"JavaScript\">alert(\"".$lib."\")</SCRIPT>";
	return $val;
}

?>

<?php
include "script.js";
?>

<BR><input type="text" id="champ1" />
<BR><input type="text" id="champ2" />
<BR><input type="button" value="update" onclick="updateValue('champ1','champ2')" />

<script language="javascript">

function updateValue ( _input, _output ){
	var _data = "input="+_input+"&output="+_output;
	// --- Retrieve value from input field
	if ( ! document.getElementById(_input) ){
		alert("champ input introuvable dans la page");
		return;
	}
	_data += "&val="+document.getElementById(_input).value;
	// --- Call PHP script to launch the treatment
	callScript("update.php",_data);
}

/**
 * Use ajax method to call PHP script and refresh screen data
 */
function callScript ( scriptName, args ){
	
	var xhr_object = null; 
	     
	if(window.XMLHttpRequest) // Firefox 
	   xhr_object = new XMLHttpRequest(); 
	else if(window.ActiveXObject) // Internet Explorer 
	   xhr_object = new ActiveXObject("Microsoft.XMLHTTP");
	else { // XMLHttpRequest non supporté par le navigateur 
	   alert("Votre navigateur ne supporte pas les objets XMLHTTPRequest..."); 
     return; 
	} 
	 
	xhr_object.open("POST", scriptName, true);
	     
	xhr_object.onreadystatechange = function() { 
	   if(xhr_object.readyState == 4) {
			//alert(xhr_object.responseText); // DEBUG MODE
			//document.write(xhr_object.responseText);
			eval(xhr_object.responseText);
		 }

		return xhr_object.readyState;
	} 
	 
	xhr_object.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
	
	xhr_object.send(args);

}

</script>

<?php
// --- Include lib where are defined functions to connect / disconnect to / from the database
include "lib.php";

$input 	= null;
$output = null;
$val		= null;

// --- Retrieve 'input' parameter data
if ( isset($_POST["input"]) && !empty($_POST["input"]) )
	$input = $_POST["input"];
// --- Retrieve 'output' parameter data
if ( isset($_POST["output"]) && !empty($_POST["output"]) )
	$output = $_POST["output"];
if ( isset($_POST["val"] && !empty($_POST["val"]) )
	$val = $_POST["val"];

// --- Controls input & output parameters	are filled
if ( $input == null || $output == null || $val == null ){
	echo "alert('Missing parameters');";
	return;
}

// --- Data are filled, so processed the treatment
$request = "SELECT field_value FROM table where val = ".$val;

// --- Connect to the database
$conn = db_connect();

if ( $conn != null ){
	// --- Execute request
	$res = @mysql_query($request,$conn);
	// ---
	$value = "";
	if ( @mysql_num_rows($res) > 0 ){
		$line = @mysql_fetch_assoc($res);
		$value = $line["field_value"];
	}
	
	// --- And modify the value of the 'output' field with the retrieved value (from the database)
	echo "var div = document.getElementById('".$output."');";
	echo "div.value = ".$value;

	// --- Disconnect from the database
	deconnect($conn,0);
}
else
 echo "alert('Connexion to the database failed');";
 
?>

$request = "SELECT field_value FROM table where val = ".$val;

$value = $line["field_value"];

echo "alert(...);";
ou
echo "var div = document.getElementBy...;";

eval(xhr_object.responseText);

	echo "div.value = ".$value;

	echo "div.value = ".$value.";";

	if ( @mysql_num_rows($res) > 0 ){
		$line = @mysql_fetch_assoc($res);
		$value = $line["field_value"];
	}

echo "div.value = ".$value.";";

echo "div.value = '".$value."';";

l'instruction if ( @mysql_num_rows($res)>0 ) ne marchais pas j'ai remplçé par if ( @mysql_num_rows($res)!=0 ) je crois que ça n'aura pas d'effet.