for cebos7 rpm

http://pkgs.org/centos-7/remi-x86_64/php-pecl-runkit-1.0.4-0.7.git5e179e9.el7.remi.5.4.x86_64.rpm.html

http://php.net/manual/en/function.runkit-function-redefine.php

<?php
function testme() {
echo "Original Testme Implementation\n";
}
testme();
runkit_function_redefine('testme','','echo "New Testme Implementation\n";');
testme();
?>