PHP中运行SQLPLUS脚本以运行Oracle查询

I am trying to connect to oracle database using SQLPLUS and php. I wrote scripts to connect. But how can i pass the SQL query to get it result in SQLPLUS?

<?php
system('sqlplus tadmin/tadmin//10.100.3.64:1521/timing',$out);
echo $out;
system('exit',$out);
echo $out;
echo 'I am done running now';
 ?>