Number comparisons in PHP 8

PHP 8 introduced significant changes to number comparisons, making them more consistent and predictable. When comparing values, PHP 8 uses number comparison for numeric types, but converts numbers to strings for string comparisons, following stricter rules.

String Categories

Strings can be categorized in three ways −

• Numeric string − Contains only numeric characters. Example − "1234" or "1.24e1".

• Leading-numeric string − Starts with numeric characters followed by non-numeric characters. Example − "12xyz" or "123 "

• Non-numeric string − Cannot be interpreted as numeric. Example − "foo" or "abc123"

PHP 7 vs PHP 8 Comparison Behavior

The most notable change is how PHP handles comparisons between numbers and non-numeric strings −

PHP 7 Behavior

0 == 'foo' // Returns true (converts string to 0)

PHP 8 Behavior

0 == 'foo' // Returns false (saner comparison)

Example

Here's a demonstration of how PHP 8 handles different string types in array keys −

<?php
    $x = [
        "1" => "first Integer",
        "0123" => "The integer index with leading 0", 
        "12str" => "using leading numeric string",
        " 1" => "using leading whitespace",
        "2.2" => "using floating number",
    ];
    print_r($x);
?>

Array
(
    [1] => first Integer
    [0123] => The integer index with leading 0
    [12str] => using leading numeric string
    [ 1] => using leading whitespace
    [2.2] => using floating number
)

Key Changes

Conclusion

PHP 8's saner string-to-number comparisons eliminate unexpected behavior where non-numeric strings were converted to 0. This makes code more predictable and reduces bugs caused by implicit type conversions.