We have an informix database, with the informix odbc driver(7.x) compiled with apache.3.1.14ssl, php 4.03.pl1. 
Our configure commands included the informix via "  --with-custom-odbc=/opt/informix  ". We do not use any of the informix ifx functions, but the php odbc functions. The code in question is as follows:
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  $crs = odbc_pconnect($host,$dblogonname,$dbpassword);
  $i = odbc_exec($crs,"set role " . $dbrole);
  $sqltxt = "select mt_id,mt_name,mt_faxattachments,mt_emlattachments, mt_text,mt_bcc, mt_faxcoverpage,mt_subject from  mail_templates where mt_id = " . $id;
  //echo("sql " . $sqlTxt . "sql");
  $rsm = odbc_exec($crs,$sqltxt);
  $rsma = odbc_fetch_row($rsm);
  $mtid = odbc_result($rsm,1);     //int
  $mtname = odbc_result($rsm,2);  // string 20
  $mtfaxattachments = odbc_result($rsm,3); // string 255
  $mtemlattachments = odbc_result($rsm,4);  // string 255
  $mttext = odbc_result($rsm,5); // text (blob)
  $mtbcc = odbc_result($rsm,6); // string 255
  $mtfaxcoverpage = odbc_result($rsm,7);   // char 8
  $mtsubject = odbc_result($rsm,8);  // char 80
  //echo("sql " . $mttext . "sql");
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Through a data base editor, the mt_text field actually had approximately 4100 characters, but the echo command  just above only displayed the first 3989 chars. Our c++ programmer can access the full field in his programs.