PHP中出现意外的T_ELSE错误 [英] Unexpected T_ELSE error in PHP

问题描述

我正在处理一本php书中的示例，并在此代码的第8行出现错误

I am working on an example from a php book and am getting an error on line 8 with this code

<?php

$agent = getenv("HTTP_USER_AGENT");
if (preg_match("/MSIE/i", "$agent"));
{
    $result = "You are using Microsoft Internet Explorer";
}
else if (preg_match("/Mozilla/i", "$agent")); 
{
    $result = "You are using Mozilla firefox";
}
else {$result = "you are using $agent"; }

echo $result;


?>

推荐答案

尝试:

$agent = getenv("HTTP_USER_AGENT");
if (preg_match("/MSIE/i", $agent)) {
  $result = "You are using Microsoft Internet Explorer";
} else if (preg_match("/Mozilla/i", $agent)) {
  $result = "You are using Mozilla firefox";
} else {
  $result = "you are using $agent";
}

echo $result;

两件事:

1. if子句的末尾有分号.这意味着随后的开括号是始终执行的局部程序段.这引起了一个问题，因为后来您有一个else语句未附加到if语句；和

1. You had a semi-colon at the end of your if clauses. That means the subsequent opening brace was a local block that is always executed. That caused a problem because later you had an else statement that wasn't attached to an if statement; and

不必执行"$agent"，因此不建议这样做.只需传递$agent.

Doing "$agent" is unnecessary and not recommended. Simply pass in $agent.

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