[php] PHP JSON String, escape Double Quotes for JS output

I'm creating a JSON string from a PHP array. I've encoded it using json_encode().

$data = array(
    'title' => 'Example string\'s with "special" characters'
);

$data = json_encode( $data );

$data is localized using wp_localize_script() and is accessible via a global data variable.

In the JS file I can access the information by the following:

var data     = data.replace( /"/g, '"' ),
    jsonData = jQuery.parseJSON( data );

console.log( jsonData );

This results in an output of:

{ "title":"Example string's with "special" characters" }

Entering that result into http://jsonlint.com/ returns an error. Removing the double quotes around "special" validates the string.

What is the best way to create a JSON string from PHP and properly escape it for use in a JS file?

I just ran into this problem and the actual issue was that I forgot to add a proper application/json header before spitting out the actual JSON data.

header('Content-Type: application/json');

This is a solutions that takes care of single and double quotes:

<?php
$php_data = array("title"=>"Example string's with \"special\" characters");

$escaped_data = json_encode( $php_data, JSON_HEX_QUOT|JSON_HEX_APOS );
$escaped_data = str_replace("\u0022", "\\\"", $escaped_data );
$escaped_data = str_replace("\u0027", "\\'",  $escaped_data );
?>
<script>
// no need to use JSON.parse()...
var js_data = <?= $escaped_data ?>;
alert(js_data.title); // should alert `Example string's with "special" characters`
</script>

Another way would be to encode the quotes using htmlspecialchars:

$json_array = array(
    'title' => 'Example string\'s with "special" characters'
);

$json_decode = htmlspecialchars(json_encode($json_array), ENT_QUOTES, 'UTF-8');

I succefully just did this :

$json = str_replace("\u0022","\\\\\"",json_encode( $phpArray,JSON_HEX_QUOT)); 

json_encode() by default will escape " to \" . But it's still wrong JSON for json.PARSE(). So by adding option JSON_HEX_QUOT, json_encode() will replace " with \u0022. json.PARSE() still will not like \u0022. So then we need to replace \u0022 with \\". The \\\\\" is escaped \\".

NOTE : you can add option JSON_HEX_APOS to replace single quote with unicode HEX value if you have javascript single quote issue.

ex: json_encode( $phpArray, JSON_HEX_APOS|JSON_HEX_QUOT ));

I had challenge with users innocently entering € and some using double quotes to define their content. I tweaked a couple of answers from this page and others to finally define my small little work-around

$products = array($ofDirtyArray);
if($products !=null) {
    header("Content-type: application/json");
    header('Content-Type: charset=utf-8');
    array_walk_recursive($products, function(&$val) {
        $val = html_entity_decode(htmlentities($val, ENT_QUOTES, "UTF-8"));
    });
    echo json_encode($products,  JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES | JSON_NUMERIC_CHECK);
}

I hope it helps someone/someone improves it.

Use json_encode($json_array, JSON_HEX_QUOT); since php 5.3: http://php.net/manual/en/json.constants.php

Error come on script not in HTML tags.

<script src="https://code.jquery.com/jquery-3.5.1.min.js"></script>
<pre><?php print_r($_POST??'') ?></pre>

<form method="POST">
    <input type="text" name="name"><br>
    <input type="email" name="email"><br>
    <input type="time" name="time"><br>
    <input type="date" name="date"><br>
    <input type="hidden" name="id"><br>
    <textarea name="detail"></textarea>
    <input type="submit" value="Submit"><br>
</form>
<?php 
/* data */
$data = [
            'name'=>'loKESH"'."'\\\\",
            'email'=>'[email protected]',
            'time'=>date('H:i:00'),
            'date'=>date('Y-m-d'),
            'detail'=>'Try this var_dump(0=="ZERO") \\ \\"'." ' \\\\    ",
            'id'=>123,
        ];
?>
<span style="display: none;" class="ajax-data"><?=json_encode($_POST??$data)?></span>
<script type="text/javascript">
    /* Error */
    // var json = JSON.parse('<?=json_encode($data)?>');
    /* Error solved */
    var json = JSON.parse($('.ajax-data').html());
    console.log(json)
    /* automatically assigned value by name attr */
    for(x in json){
        $('[name="'+x+'"]').val(json[x]);
    }
</script>