Implicit conversion from float-string “%s” to int loses precision

Description

Bitshift operators and bitwise operators work on integers, not on floats. When a string is provided, it may be converted to integer or float: in the second case, the deprecation warning is emitted.

The warning is not emitted when the conversion lands on an integer.

Example

<?php

// Extract from php-src/Zend/tests/float_to_int/warnings_string_float_literals.phpt
$var = '1.5'|3;
$var = '1.5'&3;
$var = '1.5'^3;
$var = '1.5' << 3;
$var = '1.5' >> 3;
$var = 3 << '1.5';
$var = 3 >> '1.5';

//OK : PHP is smart enough to round this to integer
((1 / 35) * 35) | 3;

//Implicit conversion from float 0.9999999999999999 to int loses precision 
//The rounding is not sufficient 
((1 / 35) * 7 * 5 ) | 3;

// valid, conversion gives an integer
$var = '14.00000000'|3;

// still valid, conversion does not handle 0.0000000000000001 precision
$var = '13.0000000000000001'|3;

?>

Literal Examples

Implicit conversion from float-string “1.5” to int loses precision
Implicit conversion from float-string “0.9999999999999999” to int loses precision

Alternatives

Cast the string to integer before using it with bitshift or bitwise operators.
Round the string to integer before using it with bitshift or bitwise operators.
Simplify the expressions before using it with bitshift or bitwise operators.

Changed Behavior

This error may appear following an evolution in behavior, in previous versions. See implicitConversionToInt

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