Using \x0A worked for me to get newline in title/tooltip on mouse hover.
FILENAME: news.php
<span onmouseover="getInfo(this,'06-APR-22')" data-html="true">Day</span>
FILENAME: news.php
<script>
function getInfo(x, dateVal) {       
      var html = $.ajax({
            type: "POST",
            url: "report/get-info.php",
            data: {             
                'dateVal': dateVal,
            },              
            success: function(response) {
                x.setAttribute('title', response );
            }
        });
}
</script>
FILENAME: get-info.php
<?php
$tmp  = $_POST['dateVal'];   
$dateVal = date("m/d/Y", strtotime($tmp));
$querySelectCode = "SELECT INFO_ID, INFO_NAME FROM INFORMATION
                    WHERE TRUNC(DP.DATE_TIME) = TO_DATE('$dateVal','MM/DD/YYYY') ";    
$stmtSelectcode = oci_parse($dbConn, $querySelectCode);
if ( ! oci_execute($stmtSelectcode) ){
    $err = oci_error($stmtSelectcode);
    trigger_error('Query failed: ' . $err['message'], E_USER_ERROR);
}
$INFO_ID = array();
while(oci_fetch($stmtSelectcode)){
    $INFO_ID[]   =  oci_result($stmtSelectcode, 'INFO_ID');
    $INFO_NAME[]     =  oci_result($stmtSelectcode, 'INFO_NAME');        
}
for($index=0 ; $index < count($INFO_ID) ; $index++)
{
    echo   $INFO_NAME[$index ] . "\x0A" ;        
}
?>