In PHP4.4.1 I noticed that gzfile only reads up to 8190 bytes per line. I had a 20K SQL query that was cut into 3 parts - and wondered why the SQL server complained. 

Reading an uncompressed file with the file() command works as expected.

This function is not binary safe. (intentionally, or not, that's the question :)

A quicker way to load a gziped file in a string :
<?php
function gzfile_get_contents($filename, $use_include_path = 0)
{
    //File does not exist
    if( !@file_exists($filename) )
    {    return false;    }
    
    //Read and imploding the array to produce a one line string
   $data = gzfile($filename, $use_include_path);
   $data = implode($data);
   return $data;
}
?>

This works similar to gzfile() but it returns the file in a string instead of an array and doesn't write it to stdout compared to readgzfile.

Note: unlike the usual file-functions filesize won't work here, since the length-parameter of gzread refers to the uncompressed length, while filesize returns the size of the compressed file.

<?php
function gzfile_get_contents($filename, $use_include_path = 0) {
    $file = @gzopen($filename, 'rb', $use_include_path);
    if ($file) {
        $data = '';
        while (!gzeof($file)) {
            $data .= gzread($file, 1024);
        }
        gzclose($file);
    }
    return $data;
}
?>