jQuery AJAX call to script fails (SugarCRM)

Clicking an icon on a webpage triggers a jQuery AJAX call to a PHP script that synchs a local database to a SugarCRM database using SOAP.

By sending myself emails before and after the problematic statements, I can see that the SOAP connection succeeds, but the ensuing login() fails without throwing a SoapFault or a normal Exception.

From the command line, it works.

Thanks in advance for any suggestions

UPDATE: some code...

//Javascript from the webpage

    url = 'http开发者_如何学C://apps.net/synch_with_CRM.php?clientGuid=141516'

     // Submit via Ajax if there aren't any errors
     jQuery.ajax({
        url: url,
        success: function(){
          jQuery("#dialog-message").dialog({
            buttons: {
            Ok: function() {
              jQuery(this).dialog('close'); /* Closes popup */
            }
          }
        })
        jQuery( "#loading_"   + crm ).hide();
        jQuery( "#icon_sync_" + crm ).show();
       }
     });

// PHP code from .../apps.net/synch_with_CRM.php

<?php
if ( $_REQUEST['clientGuid'] ) { # get the URL parameter
  $client_guid = $_REQUEST['clientGuid'];
}
else if ( $argv ) {              # get the command-line parameter
  $client_guid = $argv[$argc - 1]; # clientGuid must be last 
}

$client    = new Client( $client_guid );
$client_id = $client->GetId( );

# connection information is the same for AJAX or command-line
$connection_info = getConnectionInfo( $client_id, 'SugarCRM' );

$API_soap_client = get_connection( $connection_info );

if ( !$API_soap_client ) {
  exit( "SOAP client connection failed\n" );
}

# do other stuff here...

# SNIP!

function get_connection( $connection_info ) {
  global $soap_session_id;

  try {
    $options = array( 'location' => $connection_info['url'],
                      'uri'      => $connection_info['uri'],
                      'trace'    => 1 );

    $auth_array = array( 'user_name' => $connection_info['username'],
                         'password'  => md5( $connection_info['password'] ) );

    $API_soap_client = new soapclient( NULL, $options );

    # I get the following email whether by AJAX or command-line
    mail( 'programmer@apps.net', 'soapclient', print_r( $API_soap_client, true ) );

    $soap_session  = $API_soap_client->login( $auth_array );

    # I only get this email if the script is run from the command-line
    mail( 'programmer@apps.net', 'soap id', print_r( $soap_session, true ) );

    $soap_session_id  = $soap_session->id;

    if ( $soap_session_id != -1 ) return $API_soap_client;
    else                          return false;
  }
  catch( SoapFault $fault ) { # there is no SoapFault thrown
    mail( 'programmer@apps.net', 'soap fault', print_r( $fault, true ) );
  }
  catch( Exception $e ) {     # there is no Exception thrown
    mail( 'programmer@apps.net', 'exception', print_r( $e, true ) );

  }
} # end get_connection
?>

Anyway you could post some code to highlight the issue? Also, you may want to try doing it over REST versus SOAP since REST will be much faster.