Quick Fix After PHP MySQL Add/Insert, get key & use to ADD to 2nd File

Adding a record, then using key after record created to link 2 files. 2nd file should also use same key OR if not possible add plus using key as other field. What's possible, you tell me. mysql_connect("$hostname", "$username", "$password", "$database"); mysql_select_db("$database"); $sql = "INSERT INTO %%%%%% SET tir_clientstoreid = '".$parentstoreid."', tir_addedassoc = '".$statelaw_verifyassoc."', tir_changeassoc = '".$statelaw_verifyassoc."', tir_width = '".$pickwidth."', tir_name = '".$tirename."', tir_sidewall = '".$pickratio."', tir_rim = '".$pickrim."', tir_pending = '".$pending."', tir_invlocation = '".$invlocation."', tir_price = '".$invprice."', tir_make = '".$pickmake."', tir_addeddate = '".$nowtimestamp."' "; $res = mysql_query($sql) or die(mysql_error()); //Getting last inserted id for tbl_tires. Same id is id for tbl_tire_law_defects if (mysqli_query($conn, $sql)) { $last_id = mysqli_insert_id($conn); echo "New record created successfully. Last inserted ID is: " . $last_id; } else { echo "Error: " . $sql . "<br>" . mysqli_error($conn); } mysql_close(); mysql_connect("$hostname", "$username", "$password", "$database"); mysql_select_db("$database"); $sql = "INSERT INTO %%%%%%%% SET tir_law_id = '".$last_id."', Here's the line that I saw similar code working, but still needs changes: echo "New record created successfully. Last inserted ID is: " . $last_id; Then, the last line refers to $last_id: $sql = "INSERT INTO %%%%%%%% SET tir_law_id = '".$last_id."',