This resolves the issue with contacts created on multiple terminals.

0) concurrency issue, one contact_id was edited by 2 or more terminals
1) Better than having a new contact_id created everytime the contact_add_edit page is opened which was the behavior of the original program.
2) Still need to clean-up the code a little, and do a little bit more testing, but appears to be working nicely.
3) Still uses GET for initial setup, a todo to change.
4) Glad the bug was found, and now is fixed.

contact_add_edit.php

@@ -35,13 +35,10 @@ default:
 $page_shop_log = PAGE_SHOP_LOG . "?shop_id=$shop_id";
 
 
+// setup the proper form action and form values .. not that $_GET is such a brilliant approach :)
 if($_GET['contact_id'] == 'new_contact'){
 			
 	
-	/* Discover if previous contact creation attempt was abandoned
-		There should be at least a first and last name, if not we use
-		previous contact_id, update it and start fresh	
-	*/
 	mysql_select_db($database_YBDB, $YBDB);
 	
 	// Find previous contact_id	
@@ -50,35 +47,10 @@ if($_GET['contact_id'] == 'new_contact'){
 	$result = mysql_fetch_assoc($query);
 	$previous_contact_id = $result['previous_contact_id'];
 	
-	// If full_name is empty we will use this contact_id
-	$sql = "SELECT CONCAT(first_name, ' ', last_name) as full_name FROM contacts WHERE contact_id=" . $previous_contact_id. ";";
-	$query = mysql_query($sql, $YBDB) or die(mysql_error());
-	$result = mysql_fetch_assoc($query);		
 		
-	$full_name = $result['full_name'];
+	$new_contact_id = $previous_contact_id + 1;
-		
+	$contact_id = $new_contact_id;
-	//adds contact if new_contact is selected .. it's " " not ""
+	$contact_id_entry = 'new_contact';		
-	if ($full_name != " ") {
-		
-		$new_contact_id = $previous_contact_id + 1;
-	
-		$insertSQL = sprintf("INSERT INTO contacts (date_created) VALUES (%s)",
-							   GetSQLValueString('current_time', "date"));
-		$Result1 = mysql_query($insertSQL, $YBDB) or die(mysql_error());
-	
-		$contact_id = $new_contact_id;
-		$contact_id_entry = 'new_contact';	
-
-	} else {
-
-		$insertSQL = sprintf("UPDATE contacts SET  date_created=%s WHERE contact_id=" . $previous_contact_id,
-						   GetSQLValueString('current_time', "date"));
-		$Result1 = mysql_query($insertSQL, $YBDB) or die(mysql_error());	
-		
-		$contact_id = $previous_contact_id;
-		$contact_id_entry = 'new_contact';		
-			
-	}		
 
 	
 } elseif(isset($_GET['contact_id'])) {
@@ -90,27 +62,97 @@ if($_GET['contact_id'] == 'new_contact'){
 	$contact_id_entry = -1;
 }
 
-$editFormAction = "?contact_id={$contact_id}&shop_id={$shop_id}";
 
+$editFormAction = "?contact_id={$contact_id}&shop_id={$shop_id}";
 
 if ((isset($_POST["MM_insert"])) && ($_POST["MM_insert"] == "form1")) {
 
-	$updateSQL = sprintf("UPDATE contacts SET first_name=%s, middle_initial=%s, last_name=%s, email=%s, 
+
-  								DOB=%s, phone=%s, address1=%s, address2=%s, city=%s, 
+	/* Discover if submitted contact creation attempt is new.
-  								`state`=%s, zip=%s, pass=ENCODE(%s,'yblcatx') WHERE contact_id=%s",
+		There should be at least a first and last name.
-                    	GetSQLValueString($_POST['first_name'], "text"),
+	*/
-                    	GetSQLValueString($_POST['middle_initial'], "text"),
+	mysql_select_db($database_YBDB, $YBDB);
-                    	GetSQLValueString($_POST['last_name'], "text"),
+	
-                   	GetSQLValueString($_POST['email'], "text"),
+	$query = 'SELECT MAX(contact_id) as contact_id FROM contacts;';
-					   	GetSQLValueString($_POST['DOB'], "date"),
+	$sql = mysql_query($query, $YBDB) or die(mysql_error());	
-                    	GetSQLValueString($_POST['phone'], "text"),
+	$result = mysql_fetch_assoc($sql);	
-                    	GetSQLValueString($_POST['address1'], "text"),
+	$submitted_contact_id = $result['contact_id'] + 1;	
-                    	GetSQLValueString($_POST['address2'], "text"),
+
-                    	GetSQLValueString($_POST['city'], "text"),
+	/*
-                    	GetSQLValueString($_POST['state'], "text"),
+		$handler->debug("submitted_contact_id",$submitted_contact_id - 1);
-                    	GetSQLValueString($_POST['zip'], "text"),
+		$handler->debug("$_POST",$_POST['contact_id']);
-					   	GetSQLValueString($_POST['password'], "text"),
+		exit();
-					   	GetSQLValueString($_POST['contact_id'], "int"));
+	*/
+
+	// contact already exists it is less than $submitted_contact_id
+	if($submitted_contact_id > $_POST['contact_id']) {
+		$submitted_contact_id = $_POST['contact_id'];
+	}	
+	
+	// if contact already exists, $submitted_contact_id now equals $_POST['contact_id], and it isn't new_contact
+	if ($submitted_contact_id != $_POST['contact_id'] || $_POST === 'new_contact') {
+		$submitted_contact_id =	$_POST['contact_id'];
+	} else {
+
+		// If full_name is empty we will use this contact_id
+		$sql = "SELECT CONCAT(first_name, ' ', last_name) as full_name FROM contacts WHERE contact_id=" . $submitted_contact_id . ";";
+		$query = mysql_query($sql, $YBDB) or die(mysql_error());
+		$result = mysql_fetch_assoc($query);		
+		$full_name = $result['full_name'];
+	}
+		
+	//adds contact if new_contact is selected .. it's " " not ""
+	if (empty($full_name)) {
+		$contact_id_entry = 'new_contact';	
+	}
+
+	if ( $contact_id_entry === 'new_contact' ) {	
+	
+		// Get the actual contact_id because it may have changed on multiple terminals
+		$query = 'SELECT MAX(contact_id) as contact_id FROM contacts;';
+		$sql = mysql_query($query, $YBDB) or die(mysql_error());	
+		$result = mysql_fetch_assoc($sql);	
+		$submitted_contact_id = $result['contact_id'] + 1;			
+		
+		// Insert new contact information into a new record
+		$updateSQL = 'INSERT INTO contacts (contact_id, first_name, middle_initial, last_name, email,' . 
+													  ' phone, address1, address2, city, state, DOB, receive_newsletter, waiver, pass, zip)' .
+												' VALUES (' . 
+												$submitted_contact_id . ', ' .
+												'"' . $_POST['first_name'] . '", ' . 
+												'"' . $_POST['middle_initial'] . '", ' . 
+												'"' . $_POST['last_name']  . '", ' .
+												'"' . $_POST['email'] . '", ' .
+												'"' . $_POST['phone'] . '", ' .
+												'"' . $_POST['address1'] . '", ' .
+												'"' . $_POST['address2'] . '", ' .
+												'"' . $_POST['city'] . '", ' .
+												'"' . $_POST['state'] . '", ' .
+												'"' . $_POST['DOB'] . '", ' .
+												'"' .	$_POST['email_list'] . '", ' .
+												1 . ', ' .
+												'ENCODE("' . $_POST['password'] . '",' . '"yblcatx"), ' .
+												 '"' . $_POST['zip'] . '");';	
+	} else {
+		
+		// Update existing contact record
+		$updateSQL = sprintf("UPDATE contacts SET first_name=%s, middle_initial=%s, last_name=%s, email=%s, 
+	  								DOB=%s, phone=%s, address1=%s, address2=%s, city=%s, 
+	  								`state`=%s, zip=%s, pass=ENCODE(%s,'yblcatx') WHERE contact_id=%s",
+	                    	GetSQLValueString($_POST['first_name'], "text"),
+	                    	GetSQLValueString($_POST['middle_initial'], "text"),
+	                    	GetSQLValueString($_POST['last_name'], "text"),
+	                   	GetSQLValueString($_POST['email'], "text"),
+						   	GetSQLValueString($_POST['DOB'], "date"),
+	                    	GetSQLValueString($_POST['phone'], "text"),
+	                    	GetSQLValueString($_POST['address1'], "text"),
+	                    	GetSQLValueString($_POST['address2'], "text"),
+	                    	GetSQLValueString($_POST['city'], "text"),
+	                    	GetSQLValueString($_POST['state'], "text"),
+	                    	GetSQLValueString($_POST['zip'], "text"),
+						   	GetSQLValueString($_POST['password'], "text"),
+						   	GetSQLValueString($submitted_contact_id, "int"));
+	}
 
 	mysql_select_db($database_YBDB, $YBDB);
 	$Result1 = mysql_query($updateSQL, $YBDB) or die(mysql_error());
@@ -163,7 +205,7 @@ if ((isset($_POST["MM_insert"])) && ($_POST["MM_insert"] == "form1")) {
 
 	// Find out if any selections are in the database, 
 	// to decide whether an INSERT or DELETE needs to be done
-	$sql = "SELECT selection FROM selections WHERE contact_id=" . $_POST['contact_id'] . ";";	
+	$sql = "SELECT selection FROM selections WHERE contact_id=" . $submitted_contact_id . ";";	
 	$query = mysql_query($sql, $YBDB) or die(mysql_error());
 	$selections = [];
 	while ($result = mysql_fetch_assoc($query)) {
@@ -174,13 +216,13 @@ if ((isset($_POST["MM_insert"])) && ($_POST["MM_insert"] == "form1")) {
 		if ( is_null($selections[$interest_id]) ) {  //INSERT
 			if( !is_null($interest_checked[$selection]) ) {
 				$sql = "INSERT INTO selections (contact_id, selection, selection_value) 
-							VALUES (" .	$_POST['contact_id'] . "," . $interest_id . ",1);";			 
+							VALUES (" .	$submitted_contact_id . "," . $interest_id . ",1);";			 
 				$result = mysql_query($sql, $YBDB) or die(mysql_error());	
 			}
 		} else {	 //DELETE
 			if( is_null($interest_checked[$selection]) ) {		
 				$sql = "DELETE FROM selections WHERE selection=" . $interest_id . 
-						  " AND contact_id=" . $_POST['contact_id'] . ";";	
+						  " AND contact_id=" . $submitted_contact_id . ";";	
 				$query = mysql_query($sql, $YBDB) or die(mysql_error());		
 			}
 		}		
@@ -189,11 +231,11 @@ if ((isset($_POST["MM_insert"])) && ($_POST["MM_insert"] == "form1")) {
 	// insert as update?  But it works. 	
 	if ($_POST['comments']) {
 		$sql = "INSERT INTO selections (contact_id, selection, selection_value) 
-				VALUES (" .	$_POST['contact_id'] . ", 1,'" . $_POST['comments']  . "');";			 
+				VALUES (" .	$submitted_contact_id . ", 1,'" . $_POST['comments']  . "');";			 
 				$result = mysql_query($sql, $YBDB) or die(mysql_error());	
 	}	 	
 
-  if ($_POST['contact_id_entry'] == 'new_contact' || $_POST['contact_id_entry'] == $_POST['contact_id']){
+  if ($_POST['contact_id_entry'] == 'new_contact' || $_POST['contact_id_entry'] == $submitted_contact_id){
   
   	//navigate back to shop that it came from
 	$pagegoto = PAGE_SHOP_LOG . "?shop_id={$shop_id}&new_user_id={$contact_id}";
@@ -201,7 +243,7 @@ if ((isset($_POST["MM_insert"])) && ($_POST["MM_insert"] == "form1")) {
 
   }
 
-} 
+} // Submitted
 
 mysql_select_db($database_YBDB, $YBDB);
 $query_Recordset1 = "SELECT *, DECODE(pass,'yblcatx') AS passdecode FROM contacts WHERE contact_id = $contact_id";
@@ -222,7 +264,15 @@ $totalRows_Recordset1 = mysql_num_rows($Recordset1);
         <table border="0" cellpadding="1" cellspacing="0" bordercolor="#CCCCCC">
           <tr>
             <td><label class="contacts">Contact_id:</label></td>
-			    <td><?php echo $row_Recordset1['contact_id']; ?></td>
+			    <td>
+			    <?php 
+					if($_GET['contact_id'] == 'new_contact'){
+						echo 'New Contact';	
+					} else {
+				    	echo $row_Recordset1['contact_id']; 
+				 	}
+			    ?>
+			    </td>
 			 </tr>
           <tr >
             <td><label class="contacts">Name:</label></td>
@@ -293,7 +343,7 @@ $totalRows_Recordset1 = mysql_num_rows($Recordset1);
 				  <?php include("Connections/waiver.txt"); ?>
 				  <br />
 				  </p>
-				  </div><input id="waiver_checkbox" type="checkbox"> I agree <span id="waiver_error"></span>
+				  </div><input id="waiver_checkbox" name="waiver_checkbox" type="checkbox"> I agree <span id="waiver_error"></span>
 			  	<input type="submit" id="waiver_button" value="Show Waiver" \>
 
 				</td>
@@ -309,19 +359,27 @@ $totalRows_Recordset1 = mysql_num_rows($Recordset1);
 					<table>
 						<tr><td>&nbsp;</td></tr>
 						<?php 
-							$sql = "SELECT options.option_name AS selection FROM selections, options 
+			
-										WHERE selections.selection=options.option_name_id AND
+							if($_GET['contact_id'] != 'new_contact'){					
-										contact_id=" . $row_Recordset1['contact_id']  . ";";	
+								$sql = "SELECT options.option_name AS selection FROM selections, options 
-							$query = mysql_query($sql, $YBDB) or die(mysql_error());
+											WHERE selections.selection=options.option_name_id AND
+											contact_id=" . $row_Recordset1['contact_id']  . ";";	
+								$query = mysql_query($sql, $YBDB) or die(mysql_error());
+							}							
+							
 							$selections = [];
-							while ($result = mysql_fetch_assoc($query)) {
+							
-								$selections[$result["selection"]] = $result["selection"];		
+							if($_GET['contact_id'] != 'new_contact'){		
+								while ($result = mysql_fetch_assoc($query)) {
+									$selections[$result["selection"]] = $result["selection"];		
+								}	
 							}
 			
 							$columns = 3;
 							$c = 0;
 							$rows = 0;
 							$interest_count = count($volunteer_interests);														
+							 								 
 							 while($rows < $interest_count + 3) {				
 								echo "<tr>";							
 								
@@ -344,10 +402,13 @@ $totalRows_Recordset1 = mysql_num_rows($Recordset1);
 							}
 						?>
 						<?php if($volunteer_interest_comments) {
-									$sql = "SELECT selection_value AS comments FROM selections 
+							
-											  WHERE selection=1 AND contact_id=" . $row_Recordset1['contact_id']  . ";";
+									if($_GET['contact_id'] != 'new_contact'){	 
-									$query = mysql_query($sql, $YBDB) or die(mysql_error());
+										$sql = "SELECT selection_value AS comments FROM selections 
-									$result = mysql_fetch_assoc($query);	
+												  WHERE selection=1 AND contact_id=" . $row_Recordset1['contact_id']  . ";";
+										$query = mysql_query($sql, $YBDB) or die(mysql_error());
+										$result = mysql_fetch_assoc($query);
+									}	
 										  						
 						?>							
 						<tr><td>&nbsp;</td></tr>					
@@ -371,7 +432,15 @@ $totalRows_Recordset1 = mysql_num_rows($Recordset1);
           </table>
           
         <input type="hidden" name="MM_insert" value="form1">
-        <input type="hidden" id="contact_id" name="contact_id" value="<?php echo $row_Recordset1['contact_id']; ?>">
+        <input type="hidden" id="contact_id" name="contact_id"
+        <?php
+	        if($_GET['contact_id'] === 'new_contact'){
+					echo "value='new_contact'";	
+				} else {
+				   echo "value='" . $row_Recordset1['contact_id'] . "'"; 
+				} 
+        	?>>
+        <input type="hidden" name="email_list" id="email_list">
         <input type="hidden" name="contact_id_entry" value="<?php echo $contact_id_entry; ?>">
         </form>
 	  </tr>

js/contact.js

@@ -126,6 +126,10 @@ $(function(){
   		if (success === "Success") {
   		
 	  		var email_list = $("#email_list_toggle").val();
+			
+			// send email_list val to $_POST	  		
+	  		$("#email_list").val(email_list);
+
 	  		var waiver = waiver_checkbox.prop("checked");
 	  		if (!email_list) {
 				email_list = 0;  		
@@ -137,6 +141,9 @@ $(function(){
 	  		} else if (waiver === false) {
 	  			waiver = 0;
 	  		}
+
+			$.post("json/contact.php", {most_recent_contact_id: 1});	  		
+	  		
 			// update receive_newsletter and waiver in the database
 	  		$.post("json/contact.php", {contact_id: contact_id, email_list: email_list, waiver: waiver });
 
@@ -254,6 +261,10 @@ $(function(){
 	// beginning or stored state	
   	$.post("json/contact.php", {contact_id: contact_id, email_list_value: 1 }, function(data) {
 
+		if (data === "") {
+			data = 1;
+		}	
+	
 		$("#email_list_toggle").noUiSlider({
 			orientation: "horizontal",
 			start: data,

json/contact.php

@@ -7,6 +7,7 @@ $email_list_connector = EMAIL_LIST_CONNECTOR;
 $email_list_connector_password = EMAIL_LIST_CONNECTOR_PASSWORD;
 $ssl_certificate = SSL_CERTIFICATE;
 
+
 	// update waiver 
 	if( isset($_POST['waiver']) ) {		
 				
@@ -35,7 +36,6 @@ $ssl_certificate = SSL_CERTIFICATE;
 				$query = "UPDATE contacts SET receive_newsletter=" . $email_list .
 							" WHERE contact_id=" . $_POST['contact_id'] . ";";				 
 				$result = mysql_query($query, $YBDB) or die(mysql_error());		
-		
 	}	
 
 	// return email_list value	
@@ -80,5 +80,12 @@ $ssl_certificate = SSL_CERTIFICATE;
 						
 	}
 	
+	if(isset($_POST['most_recent_contact_id'])) {
+		$query = 'SELECT MAX(contact_id) as contact_id FROM contacts;';
+		$sql = mysql_query($query, $YBDB) or die(mysql_error());	
+		$result = mysql_fetch_assoc($sql);	
+		echo $result['contact_id'];	
+	}	
+	
 
 ?>