How to over come "blocked by CORS policy: No 'Access-Control-Allow-Origin' header"?

Content

Hi Folks,

I am calling another application's page via ajax from customer portal  and I got following error message in console

jquery.min.js:4 Access to XMLHttpRequest at 'https://abc.custhelp.com/app/pagename  ' from origin 'https://xyz.custhelp.com'; has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource

Note:

Even though I tried by including following header in php , it is not working for me.

<span class="pln" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-variant: inherit; font-weight: inherit; font-stretch: inherit; line-height: inherit; font-family: inherit; vertical-align: baseline; box-sizing: inherit; color: rgb(48, 51, 54);">header</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-variant: inherit; font-weight: inherit; font-stretch: inherit; line-height: inherit; font-family: inherit; vertical-align: baseline; box-sizing: inherit; color: rgb(48, 51, 54);">(</span><span class="str" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-variant: inherit; font-weight: inherit; font-stretch: inherit; line-height: inherit; font-family: inherit; vertical-align: baseline; box-sizing: inherit; color: rgb(125, 39, 39);">&#39;Access-Control-Allow-Origin: *&#39;</span><span class="pun" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-variant: inherit; font-weight: inherit; font-stretch: inherit; line-height: inherit;