Reliably read value of PHP display_errors - error-handling

Question

In my PHP error handler I want to do something like:
if (ini_get('display_errors') IS ON)) {
// show debug info
} else {
// show just "oops!"
}
I've look through the docs and stuff, but I can't really find out what the possible values for display_errors are (such as "on", 0, "Yes") and what it does for what value.
What should I put in place of the "IS ON" to reliably read this value?

Answer 1

I use the following code:
if (in_array(strtolower(ini_get('display_errors')), ['1', 'yes', 'on', 'true']) {
// is enabled
} else {
// is disabled
}
Or regexp
if (preg_match('/^(1|yes|on|true)$/i', ini_get('display_errors')) {
// is enabled
} else {
// is disabled
}

Answer 2

You can get the string representation of the values through ini_get(), values that display_errors can be set to is either, true\false, 0\1 and On\Off. But when user's set their php.ini it is more common to use 1 or On
if (ini_get('display_errors') == "1") {
// show debug info
}
or to check for ALL cases, you can perform a switch-case
ini_set('display_errors', 1);
switch (ini_get('display_errors')) {
case "1":
case "On":
case "true":
// show debug info
}
If you prefer the equality comparison approach, notice that ini_get returns a String value of 1, if you test the returned value with ini_get using the == with the int value 1, it becomes true. If you use the === it checks if both are equal and of the same type. String is not the same type as int so it would return false.
1 == "1"; // in PHP, this returns true, it doesn't check the type.
1 === "1"; // would be false, this however checks the type.
Using ini_get('display_errors') you can check against values like, TRUE, FALSE, and
even NULL. They will return a boolean value of either 0 which is false and anything other than 0 evaluates to true.
if (2) {
echo "2 is true!"; // echos "2 is true!"
}
I saw your comment about a discrepancy so I decided to test it myself, here is what I used
<?php
ini_set('display_errors', 1);
$verbose = ini_get('display_errors');
echo $verbose; // echo's 1
// just to test its return values.
if ($verbose) {
echo "verbose is true"; // echos "verbose is true"
}
ini_set('display_errors', 0);
$verbose = ini_get('display_errors');
echo $verbose; // echo's 0
if ($verbose) {
echo "verbose is not true"; // does not get evaluated
}
?>
This answer is a bit lengthy, but I hope this is what you need.

Answer 3

Use filter_var
if ( filter_var( ini_get('display_errors'), FILTER_VALIDATE_BOOLEAN) ){
}
And that should catch all of the different ways display_errors could get turned on ("1", "true", "on", "yes", etc.).
I also can't find any official documentation on this, but from what I've experienced, I believe using filter_var with the FILTER_VALIDATE_BOOLEAN flag will cover the full gamut of possible ways an ini setting can be set to true/false.

Answer 4

The default is '1' according to the documentation. However, you might want to check the inverse, that it isn't off:
!= FALSE or !empty()
if (ini_get('display_errors') != FALSE))
{
// show debug info
}
else
{
// show just "oops!"
}
Or as Anthony pointed out, you could just check for 1
if(ini_get('display_errors') == 1))
You might also want to check error_reporting, as it is another common setting that is used to control the displaying of errors, although its meaning is slightly different than display_errors
if(error_reporting() != 0)