As found as a comment on http://www.php.net/ziparchive:
The following code can be used to get a list of all the file names in a zip file.
<?php
$za = new ZipArchive();
$za->open('theZip.zip');
for( $i = 0; $i < $za->numFiles; $i++ ){
$stat = $za->statIndex( $i );
print_r( basename( $stat['name'] ) . PHP_EOL );
}
?>