PHP 7.4中的数值文字分隔符（Numeric Literal Separator ）

1000000000;   // Is this a billion? 100 million? 10 billion?
‪107925284.88;‬ // What scale or power of 10 is this?

$discount = 13500; // Is this 13,500? Or 135, because it's in cents?

$threshold = 1_000_000_000;  // a billion!
$testValue = ‪107_925_284.88; // scale is hundreds of millions
$discount = 135_00;          // $135, stored as cents

6.674_083e-11; // float
299_792_458;   // decimal
0xCAFE_F00D;   // hexadecimal
0b0101_1111;   // binary
0137_041;      // octal

_100; // already a valid constant name
 
// these all produce "Parse error: syntax error":
100_;       // trailing
1__1;       // next to underscore
1_.0; 1._0; // next to decimal point
0x_123;     // next to x
0b_101;     // next to b
1_e2; 1e_2; // next to e

var_dump(1_000_000); // int(1000000)