$re = '/:(?=([^\']*\'[^\']*\')*[^\']*$)/';
$str = 'select id, :DATA_INI, \':DATA_INI\', titulo,
date_format(data_criacao,\'%d/%m/%Y %H:%i\') str_data_criacao
from v$sugestoes
where data_criacao between :DATA_INI AND :DATA_FIM AND \':TEST\'
and \'test \'\'string :DATA_INI \'\' :DATA_INI \'
order by data_criacao';
$subst = "@";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php