$lastB = null;
foreach ($foo as $r) //I'm guessing that $r is the dummy variable,based on your code
{
        $b = substr($r['pon_port'],2); //You wrote this

        //This part prevents rePEtITions From happening
        if ($lastB === null || $b != $lastB) var_dump($lastB = $b);
}

(在这种情况下,我将赋值转移到参数中,使用var_dump($lastB = $b)而不是两个单独的语句.我发现它更整洁,但如果您愿意,可以将它们分开.)

如果您想要打印变量以外的其他操作,最终结果是,您可以使用以下代码：

$lastB = null;
foreach ($foo as $r) //I'm guessing that $r is the dummy variable,2); //You wrote this

        //This part PRevents repetitions from happening
        if ($lastB === null || $b != $lastB)
        {
            //do something with $b...
            $lastB = $b;
        }
}

我自己在序列“2 2 7 8 8 7”上尝试第一个代码,得到：

string(1) "2" string(1) "7" string(1) "8" string(1) "7"