In PHP 8.5, the chr() function works fundamentally the same as in previous versions, but it introduces one important update. If you pass a value outside the valid range of 0 to 255, PHP will now trigger a deprecation warning. This means you need to be a bit more careful with how you use it in your code. Here is everything you need to know about the function, along with practical examples.
What is New in PHP 8.5?
The core behavior of chr() remains the same: it returns a single-character string from a specified byte value (0-255). However, PHP 8.5 officially deprecates passing values outside this range.
The Problem with Out-of-Range Values
Previously, if you passed a number like 833 or -159, PHP would silently wrap it around to fit within the byte range. While the function will still return a result (for example, chr(833) still gives A), doing so now triggers a deprecation warning. The PHP team made this change because a single byte can only logically hold a value within that 0-255 interval.
Basic Usage (Valid Range)
You can use numbers between 0 and 255 to generate standard characters, letters, or symbols.
Example: Generating Standard Characters
<?php
// Generate the letter A (ASCII 65)
$letter = chr(65);
echo $letter; // Output: A// Generate a newline character (ASCII 10)
$newline = chr(10);
echo "Hello" . $newline . "World";
?>
Avoiding the Deprecation (Best Practice)
If you have a value larger than 255 or a negative number, and you intend to get the wrapped byte (as PHP did automatically in older versions), you should now perform the calculation manually.
Example: Using Modulo to Fix Warnings
You can use the modulo (%) operator to stay within the valid range and avoid the warning:
<?php
// In PHP 8.5, this triggers a deprecation warning:
// $char = chr(833);// Do this instead to get the same result without the warning:
$value = 833;
$char = chr($value % 256); // 833 % 256 = 65, which is A
echo $char; // Output: A
?>
Creating Special Characters
You can still use chr() to generate control characters or special symbols.
Note on Multi-byte Characters
If you are working with multi-byte characters (like Hindi text or emojis), it is always better to use the mb_chr() function instead of chr().
<?php
// Adding an escape character (ASCII 27) to a string
$str = "The string ends in escape: ";
$str .= chr(27);
echo $str;
?>
Summary
In short, the function itself is stable in PHP 8.5, but PHP now encourages stricter coding by warning you when you feed chr() a number that doesn not logically fit into a single byte. If you are passing a number outside the 0-255 range, simply use the % (modulo) operator to bring it into the valid range so your code runs perfectly without any warnings.