I'm trying to trap a user entry that cannot be found in the database. When a code is entered, the page should give a "Code Not Found" message if it is an undefined value. However, it didn't; and it always shows the "undefined" value to the page instead.

I'm really new to PHP, Javascript and AJAX, and I would greatly appreciate if you could help me on this.

Here's what I actually did:

getting user input:

<input type="text" name="fscode" size = "4" maxlength = "4" onKeyPress="return checkEnter(event,this.name,document.fchartact.locode)">

finding the code:

<?php

switch ($_GET['action']){
	case "find":
	if ($nrows == 1){
			echo $results['LOCODE'][0]."$".
				 $results['FCCODE'][0]."$".
				 $results['EXCODE'][0]."$".
				 $results['ITM'][0]."$".
				 $results['AST'][0]."$".
				 $results['IDN'][0]."$".
				 $results['SNO'][0]."$".
				 $results['QTY'][0]."$".
				 $results['NAME'][0]."$".
				 $results['CAT'][0]."$".
				 $results['EDIT'][0]."$";
	}
	else echo "not found$";
	break;
}
?>

functions called:

function checkEnter(e,obj,dest){ 
	var characterCode;
	if(e && e.which){ 
	e = e;
	characterCode = e.which; 
	}
	else{
	e = event;
	characterCode = e.keyCode;
	}
	if(characterCode == 13){
			if (this.document.fchartact.fscode.value.length == 4) 
			{
		if (obj == "fscode"){
							processcode("find");
					} 
					else if (obj == "name") {
							fs = document.fchartact.fscode.value;
							if (fs.indexOf("0") != -1) document.fchartact.save.focus(); 
							else dest.focus();
					}
					else if (obj == "edit") document.fchartact.save.click();
					else dest.focus();
					return false;
			} 
	}  
	else return true;
}
var http = getXMLHTTPRequest();
function processcode(action) {
  var coid  = document.fchartact.coidnum.value;
  var fs    = document.fchartact.fscode.value;

  var myurl = "../mas/chartajax.php";
  var param = "?fscode=" + fs + "&coidnum=" + coid + "&action=" + action;

  if (action =="save") { 
      param = param + "&locode=" + document.fchartact.locode.value 
                    + "&fccode=" + document.fchartact.fccode.value 
                    + "&excode=" + document.fchartact.excode.value  
                    + "&itm="    + document.fchartact.itm.value     
                    + "&ast="    + document.fchartact.ast.value    
                    + "&idn="    + document.fchartact.idn.value    
                    + "&sno="    + document.fchartact.snum.value   
                    + "&qty="    + document.fchartact.qty.value    
                    + "&name="   + document.fchartact.name.value   
                    + "&cat="    + document.fchartact.desc2.value  
                    + "&edit="   + document.fchartact.edit.value;
					
      if (fs=='' || document.fchartact.name.value == '') {
          alert("Please supply necessary data!");
          document.fchartact.fscode.focus();
          return false;
      }
	  
  }
	else if (action == "delete") {
		if (!confirm("Sure to delete this fscode: " + fs)) return false;
	}
   
		
	var myRand = parseInt(Math.random()*999999999999999); 
	document.fchartact.action.value = action; 
	
	modurl = myurl + param + "&rand=" + myRand;
	http.open("GET", modurl, true);
	http.onreadystatechange = getResult;
	http.send(null);
}
function getResult() {
   if (http.readyState == 4) {
    if(http.status == 200) {
       var resultlist = http.responseText.split("$");
       dispval(resultlist);
  	  }
   }
}
function dispval(res){
		var act = document.fchartact.action.value;
        
		if (act=="find") { 
			this.document.fchartact.locode.disabled = 0;
			this.document.fchartact.fccode.disabled = 0;
			this.document.fchartact.excode.disabled = 0; 
			this.document.fchartact.itm.disabled    = 0; 
			this.document.fchartact.ast.disabled    = 0; 
			this.document.fchartact.idn.disabled    = 0; 
			this.document.fchartact.snum.disabled   = 0;
			this.document.fchartact.qty.disabled    = 0; 
			this.document.fchartact.name.disabled   = 0; 
			this.document.fchartact.desc2.disabled  = 0;
			this.document.fchartact.edit.disabled   = 0;
			this.document.fchartact.locode.focus();
            alert(res[0]);
			if(res[0] == 'not found'){
					var fs = document.fchartact.fscode.value;
					var msg = fs + " not found.";
					this.document.fchartact.msg.value = msg;
					this.document.fchartact.locode.value = '';
					this.document.fchartact.fccode.value = '';
					this.document.fchartact.excode.value = ''; 
					this.document.fchartact.itm.value    = 'no'; 
					this.document.fchartact.ast.value    = 'no'; 
					this.document.fchartact.idn.value    = 'no'; 
					this.document.fchartact.snum.value   = 'no';
					this.document.fchartact.qty.value    = 'no'; 
					this.document.fchartact.name.value   = ''; 
					this.document.fchartact.desc2.value  = '';
					this.document.fchartact.edit.value   = 'no';
					this.document.fchartact.locode.focus();
			}
			else {
					this.document.fchartact.locode.value = res[0] ;
					this.document.fchartact.fccode.value = res[1];
					this.document.fchartact.excode.value = res[2]; 
					this.document.fchartact.itm.value    = res[3]; 
					this.document.fchartact.ast.value    = res[4]; 
					this.document.fchartact.idn.value    = res[5]; 
					this.document.fchartact.snum.value   = res[7];
					this.document.fchartact.qty.value    = res[6]; 
					this.document.fchartact.name.value   = res[8]; 
					this.document.fchartact.desc2.value  = res[9];
					this.document.fchartact.edit.value   = res[10];
}

I'm already having headaches trying to make this small thing work out!

I am afraid I don't really have time to read it all through, but it seems like you use the var keyword when declaring variables inside your functions: this makes the variables local. If you instead simple write the variable name and its value, the variable will be added to the window object and thus global.