Javascript code:
console.log( 1 << 5 );
console.log( 1111044149 << 2 );
Javascript output:
32
149209300
PHP code:
var_dump( 1 << 5 );
var_dump( 1111044149 << 2 );
PHP output:
32
4444176596
Why 1111044149 << 2 has difference between PHP and javascript? I'm writing a javascript code to PHP and everything worked less that part and I need the PHP code shows similar results obtained in javascript to be perfect.
The operands of a bitwise operation in JavaScript are always treated as int32, and in PHP this is not the case. So, when performing the left shift on 1111044149, this happens in JS:
01000010001110010011000000110101 (original, 32-bit)
00001000111001001100000011010100 (left shifted 2 positions, "01" is truncated)
= 149209300
And in PHP, the bits do not get truncated because it is not treated as a 32-bit integer.
Thanks for the explanations, helped me a lot and I could now make a function to handle this automatically conversion, I had forgotten that detail about 32-bit and 64-bit for lack of attention.
Function
function shift_left_32( $a, $b ) {
return ( $c = $a << $b ) && $c >= 4294967296 ? $c - 4294967296 : $c;
}
Test
var_dump( shift_left_32( 1, 5 ) );
var_dump( shift_left_32( 1111044149, 2 ) );
Output
32
149209300