在PHP 7.3.33我Apache 2.4想从 PHP（Web 服务器环境）运行 iptables 以阻止/取消阻止 IP，从命令行，这工作正常：
/usr/sbin/iptables --insert INPUT --source example.com --jump DROP
但是如果我用这段代码从 PHP 尝试：
exec('/usr/sbin/iptables --insert INPUT --source example.com --jump DROP', $return);
print_r($return);
我得到一个空白结果并且未添加 iptables 规则：
Array
(
)
但是，iptables 路径似乎正确并且 iptables 运行，因为--help命令返回内容，那么为什么上面的命令不起作用？
exec('/usr/sbin/iptables --help', $return);
print_r($return);
Array
(
[0] => iptables v1.8.4
[1] =>
[2] => Usage: iptables -[ACD] chain rule-specification [options]
[3] => iptables -I chain [rulenum] rule-specification [options]
[4] => iptables -R chain rulenum rule-specification [options]
[5] => iptables -D chain rulenum [options]
[6] => iptables -[LS] [chain [rulenum]] [options]
[7] => iptables -[FZ] [chain] [options]
[8] => iptables -[NX] chain
[9] => iptables -E old-chain-name new-chain-name
[10] => iptables -P chain target [options]
[11] => iptables -h (print this help information)
[12] =>
[13] => Commands:
[14] => Either long or short options are allowed.
[15] => --append -A chain Append to chain
[16] => --check -C chain Check for the existence of a rule
[17] => --delete -D chain Delete matching rule from chain
[18] => --delete -D chain rulenum
[19] => Delete rule rulenum (1 = first) from chain
[20] => --insert -I chain [rulenum]
[21] => Insert in chain as rulenum (default 1=first)
[22] => --replace -R chain rulenum
[23] => Replace rule rulenum (1 = first) in chain
[24] => --list -L [chain [rulenum]]
[25] => List the rules in a chain or all chains
[26] => --list-rules -S [chain [rulenum]]
[27] => Print the rules in a chain or all chains
[28] => --flush -F [chain] Delete all rules in chain or all chains
[29] => --zero -Z [chain [rulenum]]
[30] => Zero counters in chain or all chains
[31] => --new -N chain Create a new user-defined chain
[32] => --delete-chain
[33] => -X [chain] Delete a user-defined chain
[34] => --policy -P chain target
[35] => Change policy on chain to target
[36] => --rename-chain
[37] => -E old-chain new-chain
[38] => Change chain name, (moving any references)
[39] => Options:
[40] => --ipv4 -4 Nothing (line is ignored by ip6tables-restore)
[41] => --ipv6 -6 Error (line is ignored by iptables-restore)
[42] => [!] --proto -p proto protocol: by number or name, eg. `tcp'
[43] => [!] --source -s address[/mask][...]
[44] => source specification
[45] => [!] --destination -d address[/mask][...]
[46] => destination specification
[47] => [!] --in-interface -i input name[+]
[48] => network interface name ([+] for wildcard)
[49] => --jump -j target
[50] => target for rule (may load target extension)
[51] => --goto -g chain
[52] => jump to chain with no return
[53] => --match -m match
[54] => extended match (may load extension)
[55] => --numeric -n numeric output of addresses and ports
[56] => [!] --out-interface -o output name[+]
[57] => network interface name ([+] for wildcard)
[58] => --table -t table table to manipulate (default: `filter')
[59] => --verbose -v verbose mode
[60] => --wait -w [seconds] maximum wait to acquire xtables lock before give up
[61] => --wait-interval -W [usecs] wait time to try to acquire xtables lock
[62] => default is 1 second
[63] => --line-numbers print line numbers when listing
[64] => --exact -x expand numbers (display exact values)
[65] => [!] --fragment -f match second or further fragments only
[66] => --modprobe=<command> try to insert modules using this command
[67] => --set-counters PKTS BYTES set the counter during insert/append
[68] => [!] --version -V print package version.
)
