php realize the replacement of the middle digit of the cell phone number as a * and hide the last few digits of the IP method

In this article, the example of php to achieve the replacement of the middle digits of the cell phone number as * and hide the last few bits of the IP method. Shared for your reference, as follows:

$string = "13826589549";
$pattern = "/(\d{3})\d\d(\d{2})/";
$replacement = "\$1****\$3";
print preg_replace($pattern, $replacement, $string);

Output: 138****9549

This match result is what I want, but this match pattern is wrong, it can only match 7, the remaining 4 numbers can't be matched, it shows up, and \$3 doesn't exist!

The correct way to write this would be

$string = "13826589549";
$pattern = "/(\d{3})\d{4}(\d{4})/";
$replacement = "\$1****\$2";
print preg_replace($pattern, $replacement, $string);

Of course, you can also use the method of intercepting the string to hide the middle number

function suohao($phone){
 $p = substr($phone,0,3)."****".substr($phone,7,4);
 return $p;
}
echo suohao($string);

Output: 138****9549

Hide the last digits of the IP as *

<?php echo preg_replace("/[^\.]{1,3}$/","*",$ip); ?>

PS: Here are 2 more very convenient regular expression tools for your reference:

JavaScript regular expression online test tool:
http://tools./regex/javascript

Regular expression online generation tool:
http://tools./regex/create_reg

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I hope that what I have said in this article will help you in PHP programming.