how to connect to openstreetmap via the API?

How to connect to openstreetmap via the API? I really can't find normal information. I need to connect and put geo points

<?

function get_saved_locations(){
    $con=mysqli_connect ("localhost", 'root', '','locations');
    if (!$con) {
        die('Not connected : ' . mysqli_connect_error());
    }
    $sqldata = mysqli_query($con,"select lng,lat from locations ");

    $rows = array();
    while($r = mysqli_fetch_assoc($sqldata)) {
        $rows[] = $r;

    }
    $indexed = array_map('array_values', $rows);

    //  $array = array_filter($indexed);

    echo json_encode($indexed);
    if (!$rows) {
        return null;
    }
}

?>

  <script>


var map = L.map( 'map', {
  center: [57.08231,25.24116],
  minZoom: 1.5,
  zoom: 7
})

L.tileLayer( 'http://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png', {
  attribution: '&copy; <a href="https://www.openstreetmap.org/copyright">OpenStreetMap</a>',
  subdomains: ['a', 'b', 'c']
}).addTo( map )

var myURL = jQuery( 'script[src$="leaf-demo.js"]' ).attr( 'src' ).replace( 'leaf-demo.js', '' )

var myIcon = L.icon({
  iconUrl: myURL + 'images/pin24.png',
  iconRetinaUrl: myURL + 'images/pin48.png',
  iconSize: [29, 24],
  iconAnchor: [9, 21],
  popupAnchor: [0, -14]
})

for ( var i=0; i < markers.length; ++i ){
L.marker( [markers[i].lat, markers[i].lng], {icon: myIcon} )
.addTo( map );
</script>

This all works , but this is the output for JSON, and I need it from the MYSQL database, there are only 2 columns of lat lng

<?
   $con=mysqli_connect ("localhost", 'root', '','locations');
    if (!$con) {
        die('Not connected : ' . mysqli_connect_error());
    }
    // update location with location_status if admin location_status.
    $sqldata = mysqli_query($con,"select lng,lat from locations ");

    $rows = array();
    while($r = mysqli_fetch_assoc($sqldata)) {
        $rows[] = $r;

    }

?>
var tempArray = JSON.parse("[<?echo $r?>]");