PHP library object error - php

Question

I am having an issue with imagick php library.
I am doing a recursive search in my file system and look for any pdf files.
$it = new RecursiveDirectoryIterator("/test/project");
$display = Array ('pdf');
foreach(new RecursiveIteratorIterator($it) as $file){
if (in_array(strtolower(array_pop(explode('.', $file))), $display))
{
if(file_exists($file)){
echo $file; //this would echo /test/project/test1.pdf
$im = new Imagick($file);
$im->setImageFormat("jpg");
file_put_contents('test.txt', $im);
}
}
}
However, I am getting an error saying
Fatal error: Uncaught exception 'ImagickException' with message 'Can not process empty Imagick object' in /test.php:57
Stack trace:
#0 /test.php(57): Imagick->setimageformat('jpg')
#1 {main}
thrown in /test.php on line 57
line 57 is $im->setImageFormat("jpg");
However, if I replace my $im = new Imagick($file) with $im = new Imagick('/test/project/test1.pdf'), the error is gone.
I don't know why this is happening. Can someone give me a hint for this issue? Thanks so much

Answer 1

According to this, the .jpg files' format is JPEG.
Note 1:
Your $file variable is an object SplFileInfo, but you are using it always like a string. Use RecursiveDirectoryIterator::CURRENT_AS_PATHNAME flag in RecursiveDirectoryIterator's constructor, to be a real string.
Note 2:
You can filter the iterator entries with RegexIterator, f.ex.: new RegexIterator($recursiveIteratorIterator, '/\.pdf$/') (after Note 1). Or, you can use GlobIterator too for searching only pdf files.

Answer 2

As #pozs pointed out
Note 1: Your $file variable is an object SplFileInfo, but you are
using it always like a string.
Here's a code snippet which gets you the filename as string and has an optimized method to get the file extension:
<?php
$display = array ('pdf');
$directoryIterator = new RecursiveDirectoryIterator('./test/project');
// The key of the iterator is a string with the filename
foreach (new RecursiveIteratorIterator($directoryIterator) as $fileName => $file) {
// Optimized method to get the file extension
$fileExtension = pathinfo($fileName, PATHINFO_EXTENSION);
if (in_array(strtolower($fileExtension), $display)) {
if(file_exists($fileName)){
echo "{$fileName}\n";
// Just do what you want with Imagick here
}
}

Answer 3

Maybe try this approach from : PDF to JPG conversion using PHP
$fp_pdf = fopen($pdf, 'rb');
$img = new imagick();
$img->readImageFile($fp_pdf);
It also seems from reading other posts that GhostScript is faster?