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php - fwrite() 两次写入一个 json 编码的数组

问题描述

我正在尝试使用通过获取请求收集的数据编写一个 json 文件。json文件是一个二维的字符串数组，但是当数据写入文件时，嵌套数组会被写入两次。

<?php
//used for parsing html
include("simple_html_dom.php");

//read the file 
$fp = fopen("j.json", "r");
$t = fread($fp, filesize("j.json"));
fclose($fp);
$loaded = json_decode($t);

//print the loaded array
print_r($loaded);

//gathering the data
$url = "https://www.soldionline.it/quotazioni/dettaglio/IT0003934657.html";
$prezzo1 = file_get_html($url)->find("span[class=val] b", 0)->plaintext;
$data = file_get_html($url)->find("span[class=ora] b", 0)->plaintext;

$url = "https://www.soldionline.it/quotazioni/dettaglio/IT0003934657.html";
$prezzo2 = file_get_html($url)->find("span[class=val] b", 0)->plaintext;

$url = "https://www.soldionline.it/quotazioni/dettaglio/IT0003934657.html";
$prezzo3 = file_get_html($url)->find("span[class=val] b", 0)->plaintext;

//adding the new data to the array
array_push($loaded, array($prezzo1, $prezzo2, $prezzo3, $data));
//the new json string is parsed and ready to be written
$s = json_encode($loaded);

//printing stuff to ensure the data is correct
echo "<br>".$s.", type=".gettype($s)."<br>";
print_r($loaded);

//write the new json string to the same file
$fp = fopen("j.json", "w");
fwrite($fp, $s);
fclose($fp);
?>

j.json 在脚本运行之前：

[]

脚本打印的内容：

Array ( )
[["128,54","128,54","128,54","30\/12"]], type=string
Array ( [0] => Array ( [0] => 128,54 [1] => 128,54 [2] => 128,54 [3] => 30/12 ) )

脚本后的 j.json：

[["128,54","128,54","128,54","30\/12"],["128,54","128,54","128,54","30\/12"]]

我尝试像这样打开文件：$fp = fopen("j.json", "r+");然后我更改了脚本：

$s = "\"".json_encode($loaded)."\"";

echo "<br>".$s.", type=".gettype($s)."<br>";
print_r($loaded);
fwrite($fp, $s);
fclose($fp);

我发现也写了一个空值：

[]"[["128,54","128,54","128,54","30\/12"]]""null"

标签： phpjson

解决方案

浏览器在访问 url 时发送两个请求，一个对 php 文件的请求，另一个对/favicon.ico. 发送第二个请求以检查站点是否具有图标。这第二个请求导致脚本执行两次。

可以按照此处描述的步骤阻止对 favicon 的请求：https ://stackoverflow.com/a/38917888/6310593

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