Strange (buggy?) side effect of PHP 8's new string/number comparison changes

[kingIZZZY]

Relevant

• https://wiki.php.net/rfc/saner-numeric-strings
• https://wiki.php.net/rfc/string_to_number_comparison

If the intent was to have "saner numeric strings" then mission failed successfully? (or maybe only in this weird obscure case)

Description

The following code:

<?php
echo phpversion(), PHP_EOL;
var_dump("10=" > 1);
var_dump("10=" > 2);
var_dump("10=" >= 10);

Resulted in this output:

7.4.0 thru 7.4.30
bool(true)
bool(true)
bool(true)

8.0.1 thru 8.1.7
bool(true)
bool(false)
bool(true)

But I expected this output instead:

bool(true)
bool(true)
bool(true)

PHP Version

8.0.1 - 8.1.7, 7.4.0 - 7.4.30

Operating System

Ubuntu 20.04.4

[damianwadley]

Looks right to me: since "10=" is not a "well-formed numeric string", the comparison is done with both operands as strings, and lexographically "10=" comes after "1", before "2", and after "10".

[mvorisek]

IMHO, A non-numeric value encountered warning should be emit as when casting string to int implicitly - https://3v4l.org/8qkF7

[damianwadley]

But it's not casting to an int at all. That's the whole point of the change: if the string isn't a valid number then the int on the other side is converted to a string instead. No data is lost thus no warning.

[hormus]

<?php

$operand = 5;
var_dump(intval('433€')); // or explicit cast (int) or (integer) cast 433 type well-formed
var_dump(// type non well-formed,
'433€' > $operand);
var_dump($operand < '433€'
// type non well-formed,
);
/*'433€' > 5 // 4 > 5
5 < '433€' // 5 < 4*/
var_dump('433€' >= 433);
?>

From php .8.0.0 if one operand is == numeric string result is true for >=, 433€ implicit cast n length operand, if operand is 5 (one digit) less than 443€ is 4 or the same for Greater than 433€. For result true

<?php

$operand = 4;
var_dump(intval('433€')); // or explicit cast (int) or (integer) cast 433 type well-formed
var_dump(// type non well-formed,
'433€' > $operand); // true
var_dump($operand < '433€'
// type non well-formed,
); // true
/*'433€' > 4 // if first digit is 4 >= operand 4 this 433 > 4
4 < '433€' // if operand  4 <= first digit is 4 this 4 < 433*/
var_dump('433€' >= 433);
?>

https://www.php.net/manual/en/language.operators.comparison.php
If both operands are numeric strings, or one operand is a number and the other one is a numeric string, then the comparison is done numerically. These rules also apply to the switch statement. The type conversion does not take place when the comparison is === or !== as this involves comparing the type as well as the value.

[github-actions]

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[guilliamxavier]

IMHO, A non-numeric value encountered warning should be emit as when casting string to int implicitly - https://3v4l.org/8qkF7

But it's not casting to an int at all. That's the whole point of the change: if the string isn't a valid number then the int on the other side is converted to a string instead. No data is lost thus no warning.

Even without data loss, a silent behavior change is not ideal (even in a major version). A (different) warning [or notice] could be useful (but maybe annoying)?

Edit: just noticed https://wiki.php.net/rfc/string_to_number_comparison#backward_incompatible_changes and #3917