Why php file is not executed after upgrade to php 7

I am reviewing a web page that uses javascript, php, ajax and Yii framework that with php5 worked correctly, but having updated to php7 no longer works.

I comment the details belowk:

In the screen I am reviewing, MyWebPage/Folder1/protected/views/applications/file1.php is executed which assigns to the variable $load this value:

$load=‘protected/views/aplicaciones/cargas/file2.php’;

At the end of this php there is a block of code where it call several javascript libraries and then assign value to various dynamic variables, using this code:

So this php calls the file3.js javascript using this code:

This javascript theoretically calls file2.php, using this code:

        function requestData()
        {
            waitingDialog({});
            $.ajax({
                data: "startTime="+startTime+"&endTime="+endTime+"&period="+period+"&db="+db+"",
                type: "POST",
                url: loadpage,
                datatype: "json",
                success: function(data)
                {

                    closeWaitingDialog();
                    var json= eval(data);

                    // Process and paint json
                    // ...
                },

                error: function()
                {
                    closeWaitingDialog({});
                },

                cache: false
            });

With Firebug I see that loadpage = protectec/views/aplicaciones/cargas/file2.php
that looks right.

However, the problem is that after the line

var json= eval(data);

the value of json is undefined and instead of this it should contain a series of data that should be displayed on the page. These data are obtained by protectec/views/aplicaciones/cargas/file2.php, when it is executed.

From the tests I have done with Firebug the problem could be that protectec/views/applications/loads/file2.php is not being executed now, but using php 5 it is axecuted and json has correct data to show.

Any comment or suggestion is appreciated.

Obvious comment: what’s in the server side logs?

BTW is this a Yii 1.1 question?