str_replace函数如何工作？

Question

I'm trying to understand the str_replace function.

Code:

$a = array(1,8,7,5);
$b = array(3,7,11,6);
$str = '879';
$c = str_replace($a, $b , $str);
echo $c;

Output:

11119

I don't understand the output. Can someone explain how the str_replace function works?

Answer 1

str_replace replaces pair of values from provided arrays $a, $b. And does it in order, so str_replace($a, $b , $str) means:

replace 1 to 3,
then replace 8 to 7,
then replace 7 to 11
and finally replace 5 to 6.

So, let's go:

• input 879, replace 1 to 3, output 879
• input 879, replace 8 to 7, output 779
• input 779, replace 7 to 11, output 11119
• input 11119, replace 5 to 6, output 11119