关于php：socket_select立即返回false，但是没有错误代码

socket_select returns false immediately buth without error code

我正在玩socket_select，但是在一个主机上，此功能会做一些奇怪的事情：

立即返回，而不是等待5秒
返回false，表明有错误
但是socket_last_error()返回0(成功)。

此服务器的phpinfo()：http://jsfiddle.net/Lmrfe/embedded/result/

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$server = socket_create( AF_UNIX, SOCK_STREAM, 0 );
$r = socket_bind( $server, '/some/file/somewhere');
$r = socket_listen( $server );
// none of the above socket_* returns false

$t = microtime(true);
socket_clear_error();

$read = array( $server ); $write = null; $except = null;
$read = array( $server ); $write = array(); $except = array();
$read = array(); $write = array(); $except = array();
$read = null; $write = null; $except = null;

$changed = socket_select( $read, $write, $except, 5,0 );
$changed = socket_select( $read, $write, $except, null );
$changed = socket_select( $read, $write, $except, 5000000 );
$changed = socket_select( $read, $write, $except, 5000000, 0 );
$changed = socket_select( $read, $write, $except, 5000000, 5000000 );

/* Results:

microtime(true) - $t == almost zero

$changed === false

socket_last_error() === 0
socket_strerror(socket_last_error()) === Success

$read === array(1) {
[0]=>
resource(2) of type (Socket)
}
$write === NULL
$except === NULL
*/

$s = socket_read( $server, 1024, PHP_BINARY_READ );
// $s === false

这是怎么回事

更新的测试脚本：仍可立即运行：

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header('Content-Type: text/plain; charset=utf-8');
error_reporting(-1);

for( $i = 0; $i < 4; $i++ ){
for( $j = 0; $j < 5; $j++ ){
echo"\
\
\
\
\
[i,j]=[{$i},{$j}]\
";

$socket = socket_create( AF_UNIX, SOCK_STREAM, 0 );
var_dump('socket_create', $socket ); echo"\
"; if( $socket === false ) continue;

$socket_file = dirname(__FILE__)."/test_socket_i{$i}_j{$j}";
if( file_exists( $socket_file )) unlink( $socket_file );

$r = socket_bind( $socket, $socket_file );
var_dump('socket_bind', $r ); echo"\
"; if( $r === false ) continue;

$r = socket_listen( $socket );
var_dump('socket_listen', $r ); echo"\
"; if( $r === false ) continue;

$t = microtime(true);
socket_clear_error();

if($i==0){ $read = null; $write = null; $except = null; }
if($i==1){ $read = array(); $write = array(); $except = array(); }
if($i==2){ $read = array( $socket ); $write = null; $except = null; }
if($i==3){ $read = array( $socket ); $write = array(); $except = array(); }

if($j==0){ $changed = socket_select( $read, $write, $except, 5,0 ); } // 5 seconds
if($j==1){ $changed = socket_select( $read, $write, $except, null ); } // forever
if($j==2){ $changed = socket_select( $read, $write, $except, 5000000 ); }
if($j==3){ $changed = socket_select( $read, $write, $except, 5000000, 0 ); }
if($j==4){ $changed = socket_select( $read, $write, $except, 5000000, 5000000 ); }

var_dump('?socket_select returned:', $changed );echo"\
";
var_dump('?$read/$write/$except:',$read,$write,$except);echo"\
";
var_dump('?error:', socket_last_error(), socket_strerror(socket_last_error()) );echo"\
";
var_dump('time: ', microtime(true) - $t );echo"\
"; // almost zero
}}

检查一下
http://php.net/manual/zh/function.socket-select.php

Due a limitation in the current Zend Engine it is not possible to pass a constant modifier like NULL directly as a parameter to a function which expects this parameter to be passed by reference. Instead use a temporary variable or an expression with the leftmost member being a temporary variable:

所以问题是您正在初始化$write = null