pcntl_wait function hangs parent class process failed

sum = 2 o'clock why doesn't the parent process hang up?

$sum = 0;

    while(true){        $sum++;        $pid= pcntl_fork();        switch($pid){            case "-1":                echo"couldn't fork";                break;            case "0":{                var_dump(getmypid());                var_dump(pcntl_wifexited($status), pcntl_wifstopped($status), pcntl_wifsignaled($status), pcntl_wexitstatus($status), pcntl_wtermsig($status));                echo 'ppppppppp';

                exit(0);            }            default: {                if($sum == 2){                   // $subPid = pcntl_waitpid(-1, $status, SI_ASYNCIO);                   $subPid = pcntl_wait($status);                    echo '挂起'."\n";                }                var_dump('主'.getmypid());                var_dump($subPid);                echo "I'm child" . getmypid() . "\n";                echo 'ccp';                //就会执行子进程                sleep(30);                echo "\n\n\n";            }              //  exit(0);        }        var_dump(getmypid());        echo 'iiiiiii';        if($sum == 2)        break;    }            这个是答案                     string(8) "主26003"

Null
I ' m child26003
Ccpint (26004)
BOOL (TRUE)
BOOL (FALSE)
BOOL (FALSE)
Int (0)
Int (0)
Ppppppppp

Int (26003)
IIIIIII hangs
String (8) "Master 26003"
Int (26004)
I ' m child26003
Ccpint (26005)
BOOL (TRUE)
BOOL (FALSE)
BOOL (FALSE)
Int (0)
Int (0)
Ppppppppp

Int (26003)
Iiiiiii

Reply content:

sum = 2 o'clock why doesn't the parent process hang up?

$sum = 0;

    while(true){        $sum++;        $pid= pcntl_fork();        switch($pid){            case "-1":                echo"couldn't fork";                break;            case "0":{                var_dump(getmypid());                var_dump(pcntl_wifexited($status), pcntl_wifstopped($status), pcntl_wifsignaled($status), pcntl_wexitstatus($status), pcntl_wtermsig($status));                echo 'ppppppppp';

                exit(0);            }            default: {                if($sum == 2){                   // $subPid = pcntl_waitpid(-1, $status, SI_ASYNCIO);                   $subPid = pcntl_wait($status);                    echo '挂起'."\n";                }                var_dump('主'.getmypid());                var_dump($subPid);                echo "I'm child" . getmypid() . "\n";                echo 'ccp';                //就会执行子进程                sleep(30);                echo "\n\n\n";            }              //  exit(0);        }        var_dump(getmypid());        echo 'iiiiiii';        if($sum == 2)        break;    }            这个是答案                     string(8) "主26003"

Null
I ' m child26003
Ccpint (26004)
BOOL (TRUE)
BOOL (FALSE)
BOOL (FALSE)
Int (0)
Int (0)
Ppppppppp

Int (26003)
IIIIIII hangs
String (8) "Master 26003"
Int (26004)
I ' m child26003
Ccpint (26005)
BOOL (TRUE)
BOOL (FALSE)
BOOL (FALSE)
Int (0)
Int (0)
Ppppppppp

Int (26003)
Iiiiiii

