$a |= $b

Binary or operator

The bitwise or operator compares each bit of a and b.

If either bit is 1, it returns 1. Otherwise, it returns 0.

Tags
// Binary representation: 1100
$a = 12; 

// Binary representation: 1010
$b = 10; 

/*
 * Binary result: 1110 because
 * - 1 OR 1 = 1
 * - 1 OR 0 = 1
 * - 0 OR 1 = 1
 * - 0 OR 0 = 0
 */
$a |= $b; 

 1.0+

null coalescing