Missing zlib extensions on Ubuntu

February 22, 2015 10.6k views

I have a Wordpress install on a 512Mb Ubuntu 14.04 x32 which is working fine 95% of the time, however I occasionally get this error when both browsing and working in the Admin panel:

Abort class-pclzip.php : Missing zlib extensions

URL here

Can anyone help me identify what this might be? My guesses at this stage are pointed towards a plugin dependency, or php extensions but I want to confirm before playing with the config.


  • It seems some plugin is trying to use class-pclzip.php to compress or extract an archive. It might be a bug in the plugin or a missing dependency. Though, Zlib support should exist by default in Ubuntu. On the command line, what’s the output of:

     php -r 'var_dump(function_exists("gzopen"));'

    It should show bool(true) if the zlib extension is available.

  • I am having the exact same issue.

    When I run:

    php -r 'var_dump(function_exists("gzopen"));'

    in the command line, it returns bool(false).

    I ran:

    sudo apt-get install --reinstall zlibc zlib1g zlib1g-dev

    to make sure zlib is installed properly, but it’s still bool(false)

    Any suggestions on how to fix this?

  • I did the same thing, its still the same.

1 Answer

For wordpress create a file /wp-content/mu-plugins/gzopen.php with the content:

if (!function_exists('gzopen') && function_exists('gzopen64')) {
    function gzopen($filename , $mode = 'r', $use_include_path = 0 )
        return gzopen64($filename , $mode, $use_include_path);
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