"get_magic_quotes_gpc"

As I continue to ready site for php7, I'm wondering what the best replacement is for "get_magic_quotes_gpc"

You shouldn't need that. It has been removed, so you shouldn't need to account for it. If you gave me an example in context then I could tell you more, but in general it just won't be necessary anymore. It will always be false, so wherever you used to have it, you could just hard code: false, if not delete it entirely.

$colname1_rsBIBinventory = (get_magic_quotes_gpc()) ? $_POST['BPeCart6_1_SizeID_Add'] : addslashes($_POST['BPeCart6_1_SizeID_Add']);
$colname2_rsBIBinventory = (get_magic_quotes_gpc()) ? $_POST['BPeCart6_1_ColorID_Add'] : addslashes($_POST['BPeCart6_1_ColorID_Add']);
$colname3_rsBIBinventory = (get_magic_quotes_gpc()) ? $_POST['BPeCart6_1_Option1ID_Add'] : addslashes($_POST['BPeCart6_1_Option1ID_Add']);

These are lines of code associated with MySQL recordsets.... The code will be rewritten and the references to get_magic_quotes_gpc will be removed once they are updated ty MySQLi for php7.

Here is the previously updated recordset. My understanding is that the get_magic_quotes_gpc and "addslashes" were for security reasons. They are no longer necessary with mysqli? Can the complete line "$colname1_rsBIBinventory = ( get_magic_quotes_gpc() ) ? $_POST[ 'BPeCart6_1_SizeID_Add' ] : addslashes( $_POST[ 'BPeCart6_1_SizeID_Add' ] );" safely be deleted after the recordset uses mysqli?

$colname1_rsBIBinventory = ( get_magic_quotes_gpc() ) ? $_POST[ 'BPeCart6_1_SizeID_Add' ] : addslashes( $_POST[ 'BPeCart6_1_SizeID_Add' ] );
becomes:
$colname1_rsBIBinventory = $_POST[ 'BPeCart6_1_SizeID_Add' ] ;

For reference:
$query_rsBIBinventory = sprintf( "SELECT * FROM product_inventory WHERE ProductID = 23 and SizeID = %s and ColorID = %s and Option1 = %s", GetSQLValueString( $colname1_rsBIBinventory, "int" ), GetSQLValueString( $colname2_rsBIBinventory, "int" ), GetSQLValueString( $colname3_rsBIBinventory, "int" ) ); //make the query string
$rsBIBinventory = $conn_dbi->query( $query_rsBIBinventory );
$row_rsBIBinventory = $rsBIBinventory->fetch_assoc();

It will be removed when the recordset is updated to MySQLi and it will not be necessary since that protection is built in with the use of parameterized SQL statements.