The manual for json_encode specifies this:

All string data must be UTF-8 encoded.

Thus, try array_mapping utf8_encode() to your array before you encode it:

Copy$arr = array_map('utf8_encode', $arr);
$json = json_encode($arr);

// {"funds":"ComStage STOXX\u00c2\u00aeEurope 600 Techn NR ETF"}

For reference, take a look at the differences between the three examples on this fiddle. The first doesn't use character encoding, the second uses htmlentities and the third uses utf8_encode - they all return different results.

For consistency, you should use utf8_encode().

Docs

• json_encode()
• utf8_encode()
• array_map()

You are having error because of new line in your string

$string = '{"projectnumber" : "4444","projecdescription" : "4444", "articles" : [{"position":1, "article_id" : 676, "online_text" : "### Behälter; Band I-III nach indiv. Stückliste, Sprache: DE 
 - Sprache: de"},{"position":2, "article_id" : 681, "online_text" : "### Behälter; Band I-III nach indiv. Stückliste, Sprache: ### 
 - Sprache: en"}]}';


$string = preg_replace("/[\r\n]+/", " ", $string);
$json = utf8_encode($string);
$json = json_decode($json);
var_dump($json);

Output

object(stdClass)[1]
  public 'projectnumber' => string '4444' (length=4)
  public 'projecdescription' => string '4444' (length=4)
  public 'articles' => 
    array
      0 => 
        object(stdClass)[2]
          public 'position' => int 1
          public 'article_id' => int 676
          public 'online_text' => string '### Behälter; Band I-III nach indiv. Stückliste, Sprache: DE   - Sprache: de' (length=78)
      1 => 
        object(stdClass)[3]
          public 'position' => int 2
          public 'article_id' => int 681
          public 'online_text' => string '### Behälter; Band I-III nach indiv. Stückliste, Sprache: ###   - Sprache: en' (length=79)

The problem could be all character is UTF8, but json_encode does not handle it correctly.

here is a list of other characters (see Unicode characters list)

that will trigger the same error, so stripping off this one like (Å)

try below this could be help you.

htmlentities( (string) $value, ENT_QUOTES, 'utf-8', FALSE);

Change your code to:

header('Content-Type: application/json; charset=utf-8', true,200);
$JSON["today"]=array();
    
for ($i=0; $i < count($olay_tarih); $i++) { 
$gelen["date"]=array();
$gelen["content"]=array();
array_push($gelen["date"], $olay_date[$i]);
array_push($gelen["content"], $olay_content[$i]);
array_push($JSON["today"], $gelen);
}
$JSON = array_map('utf8_encode', $JSON);
echo json_encode($JSON);
        

Adding UTF-8 headers will make the browser recognize any special characters for this setting.