PHPで数値を文字列に変換する関数は何ですか?

<?php
$int_str= 123.52;
var_dump($int_str);
$str = strval($int_str);
var_dump($str);
?>

float 123.52
string '123.52' (length=6)

<?php
header(&#39;content-type:text/html;charset=utf-8&#39;);
$old = 500;
echo "原数据类型" . gettype($old), &#39;<br>&#39;;
$current = gettype(settype($old, &#39;string&#39;));
echo "现数据类型" . gettype($current), &#39;<hr>&#39;;

$old = 500.25;
echo "原数据类型" . gettype($old), &#39;<br>&#39;;
$current = gettype(settype($old, &#39;string&#39;));
echo "现数据类型" . gettype($current), &#39;<hr>&#39;;
?>

settype ( $var , $type )