Checking php extensions, functions, version, etc.

php-checks.php

<?php
echo $check_fn = ( function_exists( 'http_parse_message' ) ) ? 'yo' : 'no';
echo ' ';
echo $check_ext = ( extension_loaded( 'pecl_http' ) ) ? 'yo' : 'no';

if ( class_exists('My_Class') ) {
    $my_class = new My_Class();
}

echo 'Current PHP version: ' . phpversion();

php_info();