搜索阵列一个特定值后，怎么取代掉

$fruit = "banana";   
$fruits = array("apple","banana","orange");   
if( in_array($fruit,$fruits) ) {
       //符合条件
       //如何把$fruits的"banana"改成"pear"?
}

$fruit = "banana";   
$fruits = array("apple","banana","orange");   
if( in_array($fruit,$fruits) ) {
  $fruits[array_search($fruit, $fruits)] = "pear";
}
print_r($fruits);

Array
(
    [0] => apple
    [1] => pear
    [2] => orange
)

$fruit = "banana";   
$fruits = array("apple","banana","orange");   
if(false !== ($t = array_search($fruit, $fruits)) ) {
  $fruits[$t] = "pear";
}
print_r($fruits);