<?php
#popen.php
$process = array();
for($i=0;$i<5;$i++)
{
    echo $i.' opening ... '.chr(10);
    $process[$i] = popen('php '.dirname(__FILE__).'/popen_child.php', 'w');
    sleep(1);
}

echo 'OK>>'.chr(10);
sleep(3);
for($i=0;$i<5;$i++)
{
    $read = fread($process[$i], 64);
    echo $read;
    pclose($process[$i]);
    echo $i.' closed'.chr(10);
    sleep(1);
}

<?php
#popen_child.php
while(1)
{
    $echo =getmypid() .'->'. date("YmHis").chr(10);
    echo $echo ;
    system('echo '.$echo.'> logp');
    sleep(5);
}

例子1(popen):
<?php
function foo() {
    echo date('Y-m-d H:i:s')."\n";
    echo shell_exec('php -r \'sleep(1); echo date("Y-m-d H:i:s")." by shell_exec:blocking\n";\'');       //阻塞
    $pipe1 =  popen('php -r \'sleep(2); echo date("Y-m-d H:i:s")." by popen1:non-blocking\n";\'', 'r');  //非阻塞(管道)
    $pipe2 =  popen('php -r \'sleep(1); echo date("Y-m-d H:i:s")." by popen2:non-blocking\n";\'', 'r');  //非阻塞(管道)
    echo date('Y-m-d H:i:s')."\n";
    register_shutdown_function(function() use ($pipe1, $pipe2) { //事件驱动(脚本结束事件),异步回调
        echo stream_get_contents($pipe1); //输出子进程返回的数据
        echo stream_get_contents($pipe2); //输出子进程返回的数据
        pclose($pipe1);
        pclose($pipe2);
    });
}
foo();
//输出
2016-09-11 20:25:30
2016-09-11 20:25:31 by shell_exec:blocking
2016-09-11 20:25:31
2016-09-11 20:25:33 by popen1:non-blocking
2016-09-11 20:25:32 by popen2:non-blocking

例子2(proc_open):
<?php
function foo() {
    $proc = proc_open(
        //task.php 内容为 $arr = unserialize(stream_get_contents(STDIN)); $arr['time'] = date('Y-m-d H:i:s', $arr['time']); echo serialize($arr);
        '/png/php/5.4.45/bin/php /home/eechen/task.php', 
        array(
            0 => array('pipe','r'), //stdin (用fwrite写入数据给管道)
            1 => array('pipe','w'), //stdout(用stream_get_contents获取管道输出)
            2 => array('pipe','w'), //stderr(用stream_get_contents获取管道输出)
            //2 => array('file','/tmp/err.txt','a') //stderr(写入到文件)
        ), 
        $pipes, //管道(stdin/stdout/stderr)
        '/tmp', //当前PHP进程的工作目录
        array('foo' => 'bar') //php.ini 配置 variables_order = "EGPCS" 其中E表示$_ENV,否则$_ENV输出为空
    );
    //var_dump($pipes); //resource of type (stream)
    if(is_resource($proc)) {
        //stdin
        $stdin = serialize(array('time' => time()));
        fwrite($pipes[0], $stdin); //把参数传给脚本task.php
        fclose($pipes[0]); //fclose关闭管道后proc_close才能退出子进程,否则会发生死锁
        register_shutdown_function(function() use($pipes, $proc) { //事件驱动(脚本结束事件),异步回调
            //stdout
            $stdout = stream_get_contents($pipes[1]);
            fclose($pipes[1]);
            //stderr
            $stderr = stream_get_contents($pipes[2]);
            fclose($pipes[2]);
            //exit code (返回进程的终止状态码,如果发生错则返回-1)
            $status = proc_close($proc);
            $data = array(
                'stdout' => $stdout,
                'stderr' => $stderr,
                'status' => $status,
            );
            var_export($data); //echo json_encode($data);
        });
    }
}
foo();
//输出:
array (
  'stdout' => 'a:1:{s:4:"time";s:19:"2016-09-11 21:26:29";}',
  'stderr' => '',
  'status' => 0,
)