not necessarily. The syntax looks OK to me, what did the error say exactly? 
I am not seeing a specific error just the page will not load and it fails to update the record. If I remove the code and put it back to ((isset($_POST["busNum"]))?$_POST["busNum"]:"") the page loads fine and the record updates just not encrypted.
Here is what the code looks like when I add the AES_ENCRYPT:
$WA_fieldNamesStr = "cartoff|busCardName|busCard|busNum|busXmon|busXyear|busCode|busCardReset|payUpdate";
$WA_fieldValuesStr = "" . "|" . "".((isset($_POST["busCardName"]))?$_POST["busCardName"]:"") ."" . "|" . "".((isset($_POST["busCard"]))?$_POST["busCard"]:"") ."" . "|" . "".((isset($_POST["busNum"]))?AES_ENCRYPT($_POST["busNum"], 'encryptkey'):"") ."" . "|" . "".((isset($_POST["busXmon"]))?$_POST["busXmon"]:"") ."" . "|" . "".((isset($_POST["busXyear"]))?$_POST["busXyear"]:"") ."" . "|" . "" . "|" . "" . "|" . "";
$WA_columnTypesStr = "',none,''|',none,''|',none,''|',none,''|',none,''|',none,''|',none,''|',none,''|',none,''";
