PHP: How to check whether a library has been properly installed and enabled?

Question

Following another question on SO (I am no PHP expert), I am wondering whether the Zlib library has been properly installed on my local laptop. Documentation says there shoul

Answer 1

You can use phpinfo() to get full information about libraries

or in your PHP code test for a given function

if (function_exists("gzcompress")) {
  echo "OK";
} else {
  die("zlib missing");
}