Veriler Txt içerisinde ise

$myfile = fopen("dosya.txt", "r");
$TxtOut=fread($myfile,filesize("dosya.txt"));
fclose($myfile);
if(stristr($TxtOut,'ArananKelime')){
	echo 'Var';
}else{
	echo 'Yok';
}

Veriler Exel içerisinde ise

require('php-excel-reader/excel_reader2.php');
require('SpreadsheetReader.php');
$Deger='Yok';
$Reader = new SpreadsheetReader('example.xlsx');
$Sheets = $Reader -> Sheets();

foreach ($Sheets as $Index => $Name)
{
	$Reader -> ChangeSheet($Index);

	foreach ($Reader as $Rows)
	{
		foreach($Rows as $Row){
			if(stristr($Row,'ArananKelime')){
				$Deger='Var';
				break;
			}
		}
	}
}
echo $Deger;

Excel için gerekli dosyalar https://github.com/nuovo/spreadsheet-reader