php - Replace digits in a number with other random digits



  • I'm trying to write a function which replace four digits in a number
  • Number syntax is XX.XXXXXXX (but length may vary but min. 8 digits)
  • Digits I want to change always 5th, 6th, 7th and 8th (marked as Z --> XX.XXZZZZXXXX)
  • The number to replace Z, must be random (or 4 random digits in each Z)


x=12.3456789 --> function --> 12.34xxxx9

Where xxxx is a random number with 4 digits or four different digits.


What I've tried:

Note: I'm starting with coding... super rookie here.

function mynumber($x) {
//ok, it's not elegant but here i'm trying to get a number of 4 digits instead of digit by digit
$replacement = var_dump(random_int(1111, 9999));
//I've read about string replace but as the lenght may vary, i don't know how to delimitate the digits i want to change
$x = str_replace($x, $replacement, -?);



Usesubstr_replace() asstr_replace() will replace other matching digits not just in the 5th through 8th place:

$x = substr_replace($x, $replacement, 5, 4);

Also, you need toreturn $x; in the function. Or to modify the passed variable, you need to pass it by reference:

function mynumber(&$x) {

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