[
   {
      "PK_LINE_ITEM_ID":555,
      "DESCRIPTION":"LINE ITEM 5",
      "QUANTITY":0,
      "UNIT":"SF",
      "COST":0,
      "TOTAL":"0.00"
   },
   {
      "PK_LINE_ITEM_ID":777,
      "DESCRIPTION":"LINE ITEM 7",
      "QUANTITY":0,
      "UNIT":"SF",
      "COST":0,
      "TOTAL":"0.00"
   },
   {
      "PK_LINE_ITEM_ID":999,
      "DESCRIPTION":"LINE ITEM 9",
      "QUANTITY":0,
      "UNIT":"SF",
      "COST":0,
      "TOTAL":"0.00"
   }
]

<?php
/* Status Codes

return 0 = Nothing to Update (n/a)
return 1 = Successful Insert Query
return 2 = Database Connection refused
return 3 = MySQL Query Error OR Wrong URL Parameters */

/* Disable Warnings so that we can return ONLY what we want through echo. */
mysqli_report(MYSQLI_REPORT_STRICT);

// First get raw POST input
$raw_post     = file_get_contents('php://input');
// Run through url_decode..
$url_decoded  = urldecode($raw_post);
// Run through json_decode...
// false to allow for reference to oject. eg. $column->name instead of $column["name"] in the foreach.
$json_decoded = json_decode($url_decoded, true);

$table_name = 'tbl_xyz';

// INCLUDE DB CONNECTION STRING
include 'php_pdo_mysql_connect.php';

pdoMultiInsert($table_name, $json_decoded, $link);

function pdoMultiInsert($mysql_table, $json_decoded, $pdo_object){

//Will contain SQL snippets.
$rows_sql = array();

//Will contain the values that we need to bind.
$to_bind = array();

//Get a list of column names to use in the SQL statement.
$column_names = array_keys($json_decoded[0]);


//Loop through our $json_decoded array.
// begin outter for each
foreach($json_decoded as $array_index => $row){

$params = array();


// begin inner for each --------------------------------
foreach ($row as $column_name => $column_value) {

$param = ":" . $column_name . $array_index;

$params[] = $param;

$to_bind[$param] = $column_value;

} // end inner for each --------------------------------


$rows_sql[] = "(" . implode(", ", $params) . ")";

} // end outter for each


//Construct our SQL statement
$sql = "INSERT INTO `$mysql_table` (" . implode(", ", $column_names) . ") VALUES " . implode(", ", $rows_sql);

//Prepare our PDO statement.
$pdo_statement = $pdo_object->prepare($sql);


//Bind our values.
foreach ($to_bind as $param => $val) {

$pdo_statement->bindValue($param, $val);

}

//Execute our statement (i.e. insert the json_decoded data).
return $pdo_statement->execute();

}

$link = null;
$stmt = null;

// return 1 = Successful Insert Query
echo '1';

?>