PHP 7 - how to get usefull information from an exception message?

Question

After upgrading from PHP5 to PHP7 I get an error page saying:

0 - [] operator not supported for strings

I've read that now PHP7 is smarter with exception. But the message I get is totally useless. I don't know which file and line to look for the problem. PHP error log is also empty.

How can I get some useful error message? I'd be happy to get something like old nice fatal error saying where to fix it.

P.S. I didn't solve it from the point of view of PHP, but enabling Joomla debug in Global configuration seems to add the lost PHP error message to the output. At least this helped at another web-site in a similar situation.

Answer 1

For Joomla on php7+ non-fatal errors no longer contain the file and line in the error. The trick is to handle the output of these errors in your template's error.php file. Add the file if it doesn't exist.

With a number of templates (including beez) they will show you the stacktrace (and thus also the location of the call the threw the error) if you have debugging on, but you can customise when and how it throws the messages.

For example you could make an error.php file like:

if ($_SERVER['REMOTE_ADDR'] == $your_ip){
  echo "Error Code: " . $this->error->getCode();
  echo "<br>";
  echo htmlspecialchars($this->error->getMessage(), ENT_QUOTES, 'UTF-8');
  echo "<br><br>";
  echo $this->renderBacktrace();
}

Answer 2

The error you got after your PHP version upgrade says it loud:

the [] operator not supported for strings.

You are probably trying to push an array into a string or something of that sort.

You would have gotten an Array to string conversion error should the string in question be empty (depending on your new PHP version and as well as defined error reporting level).

The [] operator not supported for strings error occurs when you are re-declaring a string as an array or attempting to use a string as if it were an array.

Take a look at the example below (resulting in the error you have):

$me   = 'foo'; // $me is a variable holding a string value ('foo')
$me[] = 'bar'; // here, $me is re-declared as an array; an attempt to update $me with $me[]

How can you resolve this?

You simply have to re-declare your string variable just as such (still as a string variable; not as an array) for use should need be.

Take a close look at this:

$me = 'foo'; // with 'foo' as initial value when first declared
$me = 'bar'; // expected result on print_r($me) (successful, with no error): bar

Above, $me was re-assigned a new string ('bar') as value successfully and without any error.

Also, do not attempt something funny like trying to still pushing in (into your string variable, whether re-declared or not) an array or else you will get the same error.

Instead, you may convert your string into array should you want to manipulate your values as such for the purpose you seek to achieve.

Answer 3

If you can access the back end, change the Error Reporting in Global Configuration - Server to 'Maximum'. That setting will display a meaningful PHP error message which would give more information what is going wrong.

If you do not see an error-message please check if the value error_reporting is set to E_ALL in the php.ini: error_reporting=E_ALL.