search & replace text inside pdf files in php applications

new_gist_file.php

 <?php

$filePath = getcwd() . "\\Input\\MyFile.pdf";
    $fileName = basename($filePath);
    $oldText = "old text here";
    $newText = "new text here";

    //set application information
    $AppSID = "77**************";
    $AppKey = "89***********";
        
    //build URI
    echo "Uploading pdf file... <br/>";
    $strURIRequest = "http://api.saaspose.com/v1.0" . "/storage/file/" . $fileName;
    $signedURI = Sign($strURIRequest);
    uploadFileBinary($signedURI, $filePath); 
    echo "Pdf file has been uploaded successully <br/>";

    echo "Replacing text...<br/>";
    //Build JSON to post
    $fieldsArray = array('OldValue'=>$oldText, 'NewValue'=>$newText, 'Regex'=>"false");
    $json = json_encode($fieldsArray);
    //Build URI to replace text
    $strURI = "http://api.saaspose.com/v1.0" . "/pdf/" . $fileName . "/replaceText";
    $signedURI = Sign($strURI);
    $responseStream = processCommand($signedURI, "POST", "json", $json);
    $v_output = ValidateOutput($responseStream);
    if ($v_output === "")
    {
       //Save PDF file on server
       //build URI
       $strURI = "http://api.saaspose.com/v1.0" . "/storage/file/" . $fileName;
       //sign URI
       $signedURI = Sign($strURI);
       $responseStream = processCommand($signedURI, "GET", "", "");
       $outputPath = getcwd() . "\\output\\" . $fileName;
       saveFile($responseStream, $outputPath);
       echo "The text has been replaced and Pdf file has saved at: " . $outputPath;
    } 
    else 
       return $v_output;
?> 

Fatal error: Call to undefined function Sign()