Deprecated: Automatically populating $HTTP_RAW_POST_DATA is deprecated and …

Hi there,

When I add a new redirection, I get this error.
How to fix it please?

Plugin: 3.4
WordPress: 4.9.7 (single)
PHP: 5.6.32
Browser: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:61.0) Gecko/20100101 Firefox/61.0
JavaScript: https://www.PROJECT.local/wp-content/plugins/redirection/redirection.js
REST API: https://www.PROJECT.local/wp-json/

Error: JSON.parse: unexpected character at line 1 column 1 of the JSON data
Action: redirection/v1/redirect/ POST
Params: {"id":0,"url":"/agenda/","title":"","regex":false,"match_type":"url","action_type":"url","position":0,"group_id":1,"action_code":301,"action_data":{"url":"/category/news/agenda/"}}
Code: 200 OK
Raw: <br />
<b>Deprecated</b>:  Automatically populating $HTTP_RAW_POST_DATA is deprecated and will be removed in a future version. To avoid this warning set 'always_populate_raw_post_data' to '-1' in php.ini and use the php://input stream instead. in <b>Unknown</b> on line <b>0</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent in <b>Unknown</b> on line <b>0</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent in <b>/Applications/MAMP/htdocs/git/PROJECT/wp-includes/rest-api/class-wp-rest-server.php</b> on line <b>1248</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent in <b>/Applications/MAMP/htdocs/git/PROJECT/wp-includes/rest-api/class-wp-rest-server.php</b> on line <b>1248</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent in <b>/Applications/MAMP/htdocs/git/PROJECT/wp-includes/rest-api/class-wp-rest-server.php</b> on line <b>1248</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent in <b>/Applications/MAMP/htdocs/git/PROJECT/wp-includes/rest-api/class-wp-rest-server.php</b> on line <b>1248</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent in <b>/Applications/MAMP/htdocs/git/PROJECT/wp-includes/rest-api/class-wp-rest-server.php</b> on line <b>1248</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent in <b>/Applications/MAMP/htdocs/git/PROJECT/wp-includes/rest-api/class-wp-rest-server.php</b> on line <b>1248</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent in <b>/Applications/MAMP/htdocs/git/PROJECT/wp-includes/rest-api/class-wp-rest-server.php</b> on line <b>1248</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent in <b>/Applications/MAMP/htdocs/git/PROJECT/wp-includes/rest-api/class-wp-rest-server.php</b> on line <b>1248</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent in <b>/Applications/MAMP/htdocs/git/PROJECT/wp-includes/rest-api/class-wp-rest-server.php</b> on line <b>1274</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent in <b>/Applications/MAMP/htdocs/git/PROJECT/wp-includes/rest-api/class-wp-rest-server.php</b> on line <b>1248</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent in <b>/Applications/MAMP/htdocs/git/PROJECT/wp-includes/rest-api/class-wp-rest-server.php</b> on line <b>1248</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent in <b>/Applications/MAMP/htdocs/git/PROJECT/wp-includes/rest-api.php</b> on line <b>544</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent in <b>/Applications/MAMP/htdocs/git/PROJECT/wp-includes/rest-api.php</b> on line <b>545</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent in <b>/Applications/MAMP/htdocs/git/PROJECT/wp-includes/rest-api.php</b> on line <b>546</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent in <b>/Applications/MAMP/htdocs/git/PROJECT/wp-includes/rest-api.php</b> on line <b>547</b><br />
{"items":[{"id":2,"url":"\/agenda\/","action_code":301,"action_type":"url","action_data":{"url":"\/category\/news\/agenda\/"},"match_type":"url","title":"","hits":0,"regex":false,"group_id":1,"position":1,"last_access":"-","enabled":true},{"id":1,"url":"\/actualites\/","action_code":301,"action_type":"url","action_data":{"url":"\/category\/news\/actualites\/"},"match_type":"url","title":"","hits":0,"regex":false,"group_id":1,"position":0,"last_access":"-","enabled":true}],"total":2}