php array 根据value获取key,in_array()判断是否在数组内实例

<?php

header("Content-type: text/html; charset=utf-8");

$categoryids = array ('2' => '生活','103' => '法律', '104' => '宗教', '105' => '民俗' );

$isin = in_array("法律",$categoryids);

if($isin){

    echo "in====".$isin."<br>";

    echo array_search('法律',$categoryids);

}else{

    echo "out====".$isin;

}