Best way to validate uploaded Excel file data using PHPExcel - php

Question

What would be the most efficient way of checking data contained in arrays
I want to validate in the following ways:
if cell a and b are a string
if cell c and d are numbers
if cells are empty
Then how would it be best to catch errors and display them to the user?
I'm using codeigniter and the PHPExcel library
an example of where I'm currently at
public function read_excel()
{
$this->load->library('excel');
$inputFileName = 'test.xlsx';
/** Identify the type of $inputFileName **/
$inputFileType = PHPExcel_IOFactory::identify($inputFileName);
$objReader = PHPExcel_IOFactory::createReader($inputFileType);
/** Advise the Reader that we only want to load cell data **/
$objReader->setReadDataOnly(true);
/** Load $inputFileName to a PHPExcel Object **/
$objPHPExcel = $objReader->load($inputFileName);
$sheet = $objPHPExcel->getSheet(0);
$highestRow = $sheet->getHighestRow();
$highestColumn = $sheet->getHighestColumn();
// Loop through each row of the worksheet
for ($row = 2; $row <= $highestRow; $row++){ // Read a row of data into an array
$rowData = $sheet->rangeToArray('A'.$row.':'.$highestColumn.$row,NULL,TRUE,FALSE);
$cella = strtoupper($rowData[0][0]);
$cellb = strtoupper($rowData[0][1]);
$cellc = $rowData[0][2];
$celld = $rowData[0][3];
}
}
To Answer my own question i eventually went with the below
if (!isset($rowData[0][0],$rowData[0][1],$rowData[0][2])) {
echo "error cells a-c are required.";
}
for ($i=0; $i <$columns ; $i++) {
switch ($rowData[0][$i]) {
case (is_numeric($rowData[0][$i])):
filter_var($rowData[0][$i],FILTER_SANITIZE_NUMBER_INT);
echo $rowData[0][$i];
echo "</br>";
break;
case (is_string($rowData[0][$i])):
$rowData[0][$i] = preg_replace("/[^A-Za-z0-9\-]/"," ",$rowData[0][$i]);
break;
}
}