Why Does PHP\'s `json_encode` Fail with Single Quotes in Property Values?

JSON Encoding Fails with Single Quotes: A PHP Mystery

When using PHP's json_encode function to convert a stdClass object to JSON, you may encounter a puzzling failure resulting in lost property values. Let's explore this issue and uncover a solution.

The given example demonstrates the behavior:

<code class="php">$post = new stdClass();
$post->post_title = "Alumnus' Dinner Coming Soon"; // note the single quote

$json = json_encode($post);
echo $json; // outputs {"ID":"12981","post_title":null,"post_parent":"0","post_date":"2012-01-31 12:00:51"}</code>

The resulting JSON lacks the "post_title" property due to a formatting issue with the single quote. JSON's specification dictates that single quotes are not allowed within property keys or values, which json_encode strictly adheres to.

To resolve this, follow these steps:

1. Ensure UTF-8 Encoding:

Database connections must specify UTF-8 encoding to retrieve data properly. Depending on your connection method:

• Call mysql_set_charset("utf8") for the deprecated MySQL API.
• Call mysqli_set_charset("utf8") for mysqli.
• Add charset=utf8 to the connection string for PDO (PHP >=5.3.6) or execute SET NAMES utf8.

2. Decode Single Quotes:

If you encounter a character encoding issue, consider decoding single quotes explicitly. Suppose your database returned "Alumnus? Dinner Coming Soon" for "post_title":

<code class="php">$post->post_title = str_replace("\x92", "'", $post->post_title);</code>

This converts the erroneous character to a valid single quote, ensuring proper JSON encoding.

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