title: How to resolve "Call to undefined function Composer\Json\json_decode()" in PHP?
body: <p>I am in a Linux Mint system. I have install Composer. I am trying to install Laravel 4 in my www folder. I used this command <code>composer create-project laravel/laravel l4 --prefer-dist</code> at first they said I had to install mcrypt. I went to the PHP site and they said I need to install mcrypt using these commands. </p>
  
  <pre><code>apt-get install php5-mcrypt
  mv -i /etc/php5/conf.d/mcrypt.ini /etc/php5/mods-available/
  php5enmod mcrypt
  service apache2 restart
  </code></pre>
  
  <p>I have done them. Now when I try to install Laravel 4 they say </p>
  
  <blockquote>
    <p>Fatal error: Call to undefined function Composer\Json\json_decode() in phar:///usr/local/bin/composer/src/Composer/Json/JsonFile.php on line 217</p>
  </blockquote>
  
  <p>I don't know what to do now. </p>