Why doesn’t my select return in PHP?

Question

I have a PHP query which is as follows:

<?php
$serverName = "servidor";
$connectionInfo = array( "Database"=>"banco", "UID"=>"user", "PWD"=>"senha");
$conn = sqlsrv_connect( $serverName, $connectionInfo );
if( $conn === false ) {
    die( print_r( sqlsrv_errors(), true));
}

$sql = "SELECT  distinct  CONVERT(date, colunadata,103)as data FROM LISTA2 WHERE colunadata IS NOT NULL and DESCRICAO like '%valor%' GROUP BY CONVERT(date,colunadata,103)";
$stmt = sqlsrv_query( $conn, $sql );
if( $stmt === false) {
    die( print_r( sqlsrv_errors(), true) );
}

while( $row = sqlsrv_fetch_array( $stmt, SQLSRV_FETCH_ASSOC) ) {
     $dateString = $row['data']->format('d/m');
      echo $dateString."<br />";
}

sqlsrv_free_stmt( $stmt);

?>

It happens that depending on the value I put in the WHERE it works and prints on the screen the result as the "ECHO" defined above. However I put this select inside a query in SQL SERVER and returns value! Why not return some values in PHP ?