PHP / MySQL SELECT query using email address mystery -

i have particularly puzzling problem.

i using php loop through recordset , identify if email address exists in table.

the code works fine until gets 1 particular email address , can't life of me see wrong.

the email address marcodambrosio@domain.com. following error:

you have error in sql syntax; check manual corresponds mysql server version right syntax use near 'ambro'' @ line 1

all other email address fine.

i echo query

select * user_details email='marcodambrosio@domain.com' 

and run in navicat , works

php code follows:

if (!function_exists("getsqlvaluestring")) { function getsqlvaluestring($thevalue, $thetype, $thedefinedvalue = "", $thenotdefinedvalue = "")  {   if (php_version < 6) {     $thevalue = get_magic_quotes_gpc() ? stripslashes($thevalue) : $thevalue;   }    $thevalue = function_exists("mysql_real_escape_string") ? mysql_real_escape_string($thevalue) : mysql_escape_string($thevalue);    switch ($thetype) {     case "text":       $thevalue = ($thevalue != "") ? "'" . $thevalue . "'" : "null";       break;         case "long":     case "int":       $thevalue = ($thevalue != "") ? intval($thevalue) : "null";       break;     case "double":       $thevalue = ($thevalue != "") ? doubleval($thevalue) : "null";       break;     case "date":       $thevalue = ($thevalue != "") ? "'" . $thevalue . "'" : "null";       break;     case "defined":       $thevalue = ($thevalue != "") ? $thedefinedvalue : $thenotdefinedvalue;       break;   }   return $thevalue; } }  /*get source data*/ mysql_select_db($database, $link); $query_clients = "select email clients order client_id desc"; $clients = mysql_query($query_clients, $link) or die(mysql_error()); $row_clients = mysql_fetch_assoc($clients); $totalrows_clients = mysql_num_rows($clients);  {     /*check table see if email exists*/  $query_check = sprintf("select * user_details email=%s",getsqlvaluestring($row_clients['email'],"text"));  echo "<br>".$query_check."<br>";  $check = mysql_query($query_check, $link) or die(mysql_error());  if (mysql_num_rows($check)==0) {   $query_insertusers = sprintf("insert users (username, password, userlevel) values (%s, %s, 1)", $username, $password);   echo $query_insertusers."<br>";   //$insertusers = mysql_query($query_insertusers, $link) or die(mysql_error());  } } while ($row_clients = mysql_fetch_assoc($clients));  mysql_free_result($clients); 

as said - code works, when trying query 1 email address fails.

this looks escaping going wrong somehow: right syntax use near 'ambro'' seems indicate e-mail might marcod'ambrosio@domain.com. if

echo "<br>".$query_check."<br>"; 

and run that in navicat, have same error?