Dialplan:

exten => _X.,1,agi,file.php

file.php
#!/usr/bin/php -q 
<?php 
$stdin = fopen('php://stdin', 'r'); 
 $stdout = fopen('php://stdout', 'w'); 
 $stdlog = fopen('my_agi.log', 'w'); 
fputs($stdout,"SAY NUMBER 1234567\n"); 
fflush($stdout); 
?>