json_encode JSON_UNESCAPED_SLASHES not working and still escaping slashes

Question

My autocomplete search feature is broken because of how characters with accents are stored in the mySQL.

For example, in the mySQL column, É is stored like \u00c9

In the PHP, which receives the user's input and calls on mySQL, É is \xc3\x89

json_encode() almost works perfectly to take "\xc3\x89" and convert it to "\u00c9"

$clean = json_encode($criteria, JSON_UNESCAPED_SLASHES);

Except it converts it to "\\u00c9" and so the characters don't match even though they are both É.

The option JSON_UNESCAPED_SLASHES isn't working. Why does it not keep another backslash from being added in front of the backslash?

How do I get this to work?

Edit: I just added the actual code and error log output below. code:

error_log("criteria vvvvvvvvvvvvv");
error_log($criteria);

$clean = json_encode($criteria, JSON_UNESCAPED_SLASHES);  

error_log("json_encode(criteria) vvvvvvvvvvvvvv");
error_log($clean);

The error log:

[Fri Aug 23] criteria vvvvvvvvvvvvvvv, 
[Fri Aug 23 \xc3\x89
[Fri Aug 23] json_encode(criteria) vvvvvvvvvvvvvvv, 
[Fri Aug 23] "\\u00c9"

Answer 1

First JSON_UNESCAPED_SLASHES is used to prevent escaping "SLASHES" / as the name implies, don't expect it to prevent escaping backslashes \

echo json_encode('/'); // prints "\/"
echo json_encode('/', JSON_UNESCAPED_SLASHES); // prints "/"
echo json_encode("\\", JSON_UNESCAPED_SLASHES); // prints "\\"
//note on line 3 : the input is 1 backslash

As you can see it prevents escaping slashes only , not backslashes

Regarding your problem, if you ended up by using json_encode with something like \\u00c9 then you must have gave it this string as input \u00c9 , json_encode() did nothing wrong , you feed it with the string "\u00c9" not the Unicode character00c9 and it escaped the backslash at the string beginning.

Your $criteria variable is probably holding a JSON encoded string like "\u00c9" that has been encoded without using the JSON_UNESCAPED_UNICODE option, in other words don't use json_encode() twice.

check these examples, it could clear things out

echo json_encode("É", JSON_UNESCAPED_SLASHES) . "\n";
echo json_encode("\u00c9", JSON_UNESCAPED_SLASHES) . "\n";
echo json_encode("\xc3\x89", JSON_UNESCAPED_SLASHES) . "\n";
echo json_encode("/") . "\n";
echo json_encode("/", JSON_UNESCAPED_SLASHES) . "\n";
echo json_encode("\\", JSON_UNESCAPED_SLASHES) . "\n";

This outputs

"\u00c9"
"\\u00c9"
"\u00c9"
"\/"
"/"
"\\"

live demo