PHP 8.0: +/- operators take higher precedence when used with concat (.) operator

PHP 7.3 deprecated unparenthesized expressions containing '.' and '+'/'-'. From PHP 8.0, operator precedence is enforced, and this deprecation notice is no longer raised.

When an expression contains the contact operator (.) and +/- operators, +/- operators take precedence.

For example, consider the following snippet:

echo 35 + 7 . '.' . 0 + 5;

Prior to PHP 8, this snippet will be evaluated in the order of the operators. From PHP 8.0 and later, the + and - operators take a high a precedence. If you have been ignoring the deprecation notices since PHP 7.3, you can have different results:

Pre-PHP 8

echo 35 + 7 . '.' . 0 + 5;
// Deprecated: The behavior of unparenthesized expressions containing both '.' and '+'/'-' will change in PHP 8: '+'/'-' will take a higher precedence in /in/n3lVl on line 3 
// 47

PHP 8 and later

echo 35 + 7 . '.' . 0 + 5;
// 42.5

This is equivalent to (35 + 7) . '.' . (0 + 5).

Backwards compatibility impact

If you have any existing code that raised a deprecation notice due to expressions that contained . and +/- operators in same expression without parenthesis, note that the output of in PHP 8 can be different.

Make sure to properly add paranthesis to your existing expressions to express their meaning.

- echo 35 + 7 . '.' . 0 + 5;
+ echo (35 + 7) . '.' . (0 + 5);