PHP如何将数组转换成JSON？

在PHP中可以通过使用函数“json_encode()”将数组转为JSON，该函数的作用是对变量进行JSON编码，函数语法为“json_encode($val)”，返回值为JSON编码的字符串。

使用示例

<?php
$a = array('<foo>',"'bar'",'"baz"','&blong&', "\\xc3\\xa9");

echo "Normal: ",  json_encode($a), "\\n";
echo "Tags: ",    json_encode($a, JSON_HEX_TAG), "\\n";
echo "Apos: ",    json_encode($a, JSON_HEX_APOS), "\\n";
echo "Quot: ",    json_encode($a, JSON_HEX_QUOT), "\\n";
echo "Amp: ",     json_encode($a, JSON_HEX_AMP), "\\n";
echo "Unicode: ", json_encode($a, JSON_UNESCAPED_UNICODE), "\\n";
echo "All: ",     json_encode($a, JSON_HEX_TAG | JSON_HEX_APOS | JSON_HEX_QUOT | JSON_HEX_AMP | JSON_UNESCAPED_UNICODE), "\\n\\n";

$b = array();

echo "Empty array output as array: ", json_encode($b), "\\n";
echo "Empty array output as object: ", json_encode($b, JSON_FORCE_OBJECT), "\\n\\n";

$c = array(array(1,2,3));

echo "Non-associative array output as array: ", json_encode($c), "\\n";
echo "Non-associative array output as object: ", json_encode($c, JSON_FORCE_OBJECT), "\\n\\n";

$d = array('foo' => 'bar', 'baz' => 'long');

echo "Associative array always output as object: ", json_encode($d), "\\n";
echo "Associative array always output as object: ", json_encode($d, JSON_FORCE_OBJECT), "\\n\\n";
?>
以上例程会输出：
Normal: ["<foo>","'bar'","\\"baz\\"","&blong&","\\u00e9"]
Tags: ["\\u003Cfoo\\u003E","'bar'","\\"baz\\"","&blong&","\\u00e9"]
Apos: ["<foo>","\\u0027bar\\u0027","\\"baz\\"","&blong&","\\u00e9"]
Quot: ["<foo>","'bar'","\\u0022baz\\u0022","&blong&","\\u00e9"]
Amp: ["<foo>","'bar'","\\"baz\\"","\\u0026blong\\u0026","\\u00e9"]
Unicode: ["<foo>","'bar'","\\"baz\\"","&blong&","é"]
All: ["\\u003Cfoo\\u003E","\\u0027bar\\u0027","\\u0022baz\\u0022","\\u0026blong\\u0026","é"]

Empty array output as array: []
Empty array output as object: {}

Non-associative array output as array: [[1,2,3]]
Non-associative array output as object: {"0":{"0":1,"1":2,"2":3}}

Associative array always output as object: {"foo":"bar","baz":"long"}
Associative array always output as object: {"foo":"bar","baz":"long"}

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